To enable one kind of toilet to cope with two different washing systems.

In the case a drain socket connecting a drain pipe provided to construction floor surface, etc., to an exhaust section of the toilet 1 adopts a siphon washing system, the drain socket having a small orifice with the minimum inside diameter in the middle part thereof is used, and in the case a non- siphon washing system is adopted, a large drain socket with the minimu inside diameter is used. In a non-siphon washing drain socket, in order to cause a gentle siphon operation, it has no orifice section or has the inside diameter not to be much throttled. An expanded space section 4 equipped with an upper side 4a located upward of the top of a drain 3 is formed in the middle part of the curved drain 3 continued to a trap section 2. By the constitution, pseudo siphon action causing seal-breaking sound is generated, and as a result, washing noises is reduced.