PURPOSE: To improve the mechanical strength at the connecting part between a main body case and toilet lid or toilet seat.

CONSTITUTION: A main body case 2 and toilet lid 3 are rotatably connected by a collar 7. At the same time, the rotating shaft 12 of a toilet lid rotation reducer 11 which is arranged in the main body case 2 is provided in such a manner that the rotating shaft 12 may go through the inside of the collar 7. Hence a part of the shear load by the self weight of the toilet lid 3 or accompanying with usage is borne by the collar 7, and the mechanical strength of the connected part is improved. At the same time, the rotating shaft 12 is prevented from being exposed, and the mechanical strength is prevented from decreasing due to a detergent, etc.