To easily replace and fit various members in accordance with changes of users' liking or physical functions afterward by connecting a panel to which various members such as a back seat, an armrest, a housing caninet, etc., can be selectively attached at the rear part of a western style toilet stool body.

A back seat member 3, a washing unit 4 for the private parts, and a toilet seat 5 are detachably and exchangeably attached to a western style toilet stool body 1 or a panel 2. This toilet stool can be used as usual by only attaching the soilet seat 5 to the western style toilet stool body 1 and the panel 2. When various kinds of members such as an armrest or the like are required afterward in accordance with changes of user's liking or physical functions, other members can be easily exchanged while the western style toilet stool body 1 and the panel 2 are used as they are. In this case, since the stool body 1 and the panel 2 can be used as common members, the management becomes simple.