The age up to which a child can use the large bath with the parent of the other gender differs by place.
In many places, and at Atami's day-use onsen, baths are separate by gender from age 7
Japanese onsen large baths are split into a men's bath and a women's bath, and children too go into one or the other depending on their age. Japan does not set one national age for how long a child may go in with the parent of the other gender; it is set by prefectural ordinances. So that you are not left wondering, when you arrive at an onsen hotel and head for the large bath before dinner, whether a father can take his daughter in or a mother her son, this article draws the line from the national guidance and the prefectural rules, and sets out how a family of 6 with grandparents can split up and which baths to choose if you want to bathe together.
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National and prefecturalThe national government only gives guidance; prefectural ordinances set the line (age 7, age 8 or no age stated)
In short: the national government only gives the guidance that "boys and girls of about 7 and over should not be allowed to bathe with the other gender (go into the same bath as people of the other gender)", and the actual age is set by prefectural (in places, city) ordinances. As of April 2025, for public baths such as day-use onsen, 33 prefectures draw the line at age 7 and over, 5 at age 8 and over, and 9 have no age stated in their ordinance.
| Separate from | Number of prefectures | Main places |
|---|---|---|
| Age 7 and over | 33 | Tokyo, Kanagawa, Shizuoka, Hyogo, Oita and others |
| Age 8 and over | 5 | Aichi, Shiga, Tottori, Kumamoto, Miyazaki |
| No age stated in the ordinance | 9 | Fukushima, Chiba, Niigata, Osaka, Nara, Shimane, Hiroshima, Yamaguchi, Saga (Osaka sets it not by ordinance but in the prefecture's own guideline, which it changed to age 7 and over in March 2021) |
- The national (MHLW) hygiene guidelines for public baths and inns say "do not allow boys and girls of about 7 and over to bathe with the other gender". These guidelines are technical advice to prefectures, and the law leaves the standards for bathing rules to prefectures to set by ordinance.
- The national guidance used to be "about 10 and over". It came down to 7 around 2020, and local ordinances have been revised one after another since.
- As of January 2021, 28 prefectures drew the line at age 10 and over and 4 at age 12 and over. Even if an old travel blog or review says "children can go in together until 10", in many places that no longer holds.
- Among the onsen towns on this site, Hakone (Kanagawa), Kinosaki (Hyogo) and Beppu (Oita) are age 7 and over, and Echigo-Yuzawa (Niigata) has no age stated in the ordinance.
- No age in the ordinance does not mean a child of any age may go in with you. The facility may set its own line.
At Atami (Shizuoka) day-use onsen, children aged 7 and over bathe separately by gender
In short: Shizuoka Prefecture revised its ordinance and, from 1 October 2023, lowered the age from which children may not bathe with the other gender in public baths from "10 and over" to "7 and over". At Atami's day-use onsen, children aged 7 and over bathe separately by gender.
- For the large baths at Atami's onsen hotels, the national guidance is the same age 7. Check each property's rules in its guidance, as in the next section.
- Shizuoka City and Hamamatsu City also changed to age 7 and over from the same date, 1 October 2023, for both inns and public baths. Atami City comes under the prefecture, with a different ordinance from Shizuoka City and Hamamatsu City.
- Tokyo also changed from 10 and over to 7 and over from 1 January 2022.
- How 6 can stay at an Atami property is in a big family of 6 in one room in Atami. The open-air bath "Shima no Yu" on Hatsushima, the island you reach by boat from Atami, is also separate by gender (a day crossing from Atami to Hatsushima with a big family of 6).
Accommodation may draw a stricter line than the ordinance (some go by height)
In short: at hotel and ryokan large baths, the property may set its own line, and some go by height as well as age. When you book, read the notes on the plan.
- In plan notes on booking sites, some properties ask that children aged 7 and over or 120 cm and taller use the bath for their own gender.
- A tall 6-year-old may have to bathe separately because of height, even in a place where their age would allow them in together.
- The line may change as ordinances are revised. It may not be the same as when you last stayed.
If unsure, ask at the front desk when you check in (show it in Japanese):
この子は〇歳です。
父親と一緒に男湯に入れますか？
(Meaning: This child is _ years old. Can they go into the men's bath with their father?) For a mother and son, ask 「母親と一緒に女湯に入れますか？」 (Can they go into the women's bath with their mother?).
Splitting a family of 6With grandparents to go along, a family of 6 can split up without trouble
The example family in this article is 6 people: parents, 2 children (elementary school) and grandparents.
In short: if you split up as father + grandfather + son and mother + grandmother + daughter, the age line does not get in the way. The only difficult case is one parent alone taking a child of the other gender in. With three generations, the grandparents can be the ones who go along.
This split assumes the MHLW guidance and a prefectural ordinance that separates children by gender from age 7. If the property sets its own line (such as height), follow that (as of October 2026).
- If you have a child aged 7 or over, plan on splitting up in the large bath.
- Onsen rules on tattoos are in onsen and tattoo etiquette at Echigo-Yuzawa.
To bathe all together, choose a private bath or a bath in your room
In short: if you want to bathe all together, choose a private bath (family bath), which only your family uses for a set time, or a bath attached to your room. At many properties the whole family can use these together (check the property's guidance).
- Whether you need to book, whether there is a charge and how many people can go in differ by property.
- With a room that has its own bath, you can bathe whenever suits the family.
- How to choose a property with a private bath is in places to stay with a family bath in Beppu, and properties in Atami where 6 can stay in one room are in a big family of 6 in one room in Atami.
Honest notes (4 things we could not confirm or did not include)
These are things we have not been able to verify, so we do not assert them.
The ordinance age for Atami onsen hotel large baths
We could not find the official text showing whether Shizuoka Prefecture's inn ordinance has an age rule for bathing with the other gender. This article only states that Atami's day-use onsen (public baths) separate children aged 7 and over by gender, and that for hotel large baths the national guidance is also age 7.
How "age 7" is counted
We have not confirmed the basis for whether age 7 is counted as full years of age. This article only says "7 and over".
Each property's age and height line
We have not confirmed the large bath rules (age, height) of individual properties in Atami on their official sites. We give the example from booking site notes without naming the property.
The number of prefectures
The ages by prefecture come from the Research Institute for Local Government survey (as of 1 April 2025, public baths); we did not check each prefecture's ordinance text one by one. They may have changed with later revisions.
Japanese onsen and children's ages FAQ
In Japan, up to what age can a child go into an onsen with the parent of the other gender?
There is no single national rule. The national guidance is that children of about 7 and over should not bathe with the other gender, and the actual age is set by prefectural ordinances. Many places separate at age 7, and public baths in Shizuoka (Atami) and Tokyo are also age 7 and over.
Can a father take his 6-year-old daughter into the large bath at an Atami onsen hotel?
Atami's day-use onsen (public baths) separate children aged 7 and over by gender, so a 6-year-old can go in together. For hotel large baths the national guidance is the same age 7, but the property may set its own rules, and some go by height. Check when you check in.
Can a mother take her 8-year-old son into the women's bath?
Whether the place separates at age 7 (Shizuoka, Tokyo and others) or at age 8 (Aichi, Kumamoto and others), an 8-year-old cannot go into the women's bath at a day-use onsen. For a property's large bath, check its guidance. Going into the men's bath with his father or grandfather, or using a private bath, is the sure way.
Can the whole family go into a private bath?
A private bath is one your family uses alone for a set time, so at many properties the whole family can use it together. How many people can go in and how to book differ by property, so read its guidance.
In places like Chiba or Niigata with no age stated in the ordinance, can a child of any age go in together?
No. Even with no rule in the ordinance, the facility or property may set its own line. Read the guidance of the place you go to, or ask at reception.
📍 One of the articles in our Atami trip plan (Atami | Trip plan for large families / all tips articles)