To unnecessitate the wiping-off work of deposits on the inner surface of a tank and the pouring of water into the tank by providing a synthetic resin-made inner bag which is arranged in the tank so as to be freely attachable/detachable, communicates with a stool with a first introduction port by means of piercingly arranging two introduction ports and is provided with a dip-up tube which is inserted to the second introduction port.

In a toilet, the first and the second introduction ports 20a and 20b are piercingly arranged and the inner bag 20 is arranged inside the tank 10 so as to be freely attachable/detachable. The inner bag 20 communicates with the stool A through the first introduction port 20a consisting of a connecting pipe Tp fixed to the throat part T of the stool A and a flange part F1 fixed to the inner bag 20. The dip-up tube V is inserted to the second introduction port of the inner bag 20, a lid C is disposed to clog the second introduction port 20b so as to be freely attachable/detachable and the upper end of the dip-up tube V is adopted as a dip-up port H. The first flange F1 forming a hub F1a is arranged in the connecting pipe Tp fixed to the throat part T and a support part F1b is integrally formed with the hub F1a in the first flange F1.