To automatically supply flushing water at an arbitrary frequency, by providing a means discriminating a supply timing of flushing water on the basis of the compared result of a preset value with a measured value and outputting a water supply signal.

A used time signal T and a used number signal N from a counting means 31 are compared in the length of time and the frequency with a preset signal Ts of using time and a preset signal Ns of using number to output an under preset value signal L and an above preset value signal G. The signals L, G are discriminated on the basis of preset discriminating conditions like the supplying time and conditions of flushing water, in a discriminating means 34 and a water supply signal D is output to accelerate flushing of water. The supply volume and time of flushing water proportional to the used time or accumulated time of a toilet seat are calculated on the basis of a water supply instruction signal F from the preset means 33, in a water volume computing mean 35, and a supply signal W of flushing water corresponding to the actual supply volume and time of the flushing water is transmitted to the water supply means 5.