PURPOSE: To enable even general water-soluble paper which is not specially worked for a seat sheet, to be certainly retained by setting a seat sheet retaining device for enabling a case for retaining the seat sheet on a seat, and a case for retaining no closet seat sheet on the seat, to be switched to each other.

CONSTITUTION: A seat 1 is provided with a seat sheet retaining device for enabling the case of retaining a seat sheet 3 and the case of retaining no seat sheet to be switched to each other. In this seat sheet retaining device, through the surface of the seat, a plurality of small slots 8 are bored, and on the surface or in the internal section of the closet seat 1, a hollow section 9 is formed, and the hollow section 9 and the slots 8 communicate with each other, and the hollow section 9 is connected to a suction and exhaust pump 11. As this result, even general water-soluble paper which is not specially worked for the seat sheet can be certainly retained, and the seat can be used also without the closet seat sheet.