To compact arrange an upstair drain pipe room through which an upstair drain pipe absolutely necessary to effectively use a toilet room of three- story housing, etc., is arranged, on a side part of a toilet cabinet.

A toilet cabinet A positioned on a rear part of a flush toilet stool and positioned within width of a toilet room is constituted in the toilet room with the flush toilet stool B arranged in it, and an upstair drain pipe room K through which an upstair drain pipe of the flush toilet stool B passes is arranged vertically along the toilet room on a side part of the toilet cabinet A. Additionally, the inside of the toilet cabinet A is separated up and down by a tank placing base, an upper part is made a low tank storage space in which a low tank is arranged and a lower part is constituted to be a drain pipe room in which a drain pipe is arranged. Furthermore, a washhand basin is exposed and arranged on an upper surface of the toilet cabinet A above the low tank storage space.