PURPOSE: To detect a seating without fail by a method wherein when a user sits on a toilet seat of western style, an output of a high-frequency oscillator which is changed by electrostatic capacity of a human body is amplified, filtered and compared with a reference voltage.

CONSTITUTION: An electrode 44 of alumium film is embedded in the rearside of a toilet seat, connected to an output terminal of a crystal oscillator 62, and further connected to a base of a transistor Tr60 of a high frequency oscillating circuit 50. When a user sits on a seat, electrostatic capacity 64 by a human body is connected in parallel to a crystal oscillator 62, a base voltage of the transistor Tr60 goes down and an output of the oscillator 50 also goes down. The output signal of the oscillator 50 is filtered by a BPF 52, averaged and compared with a reference voltage 56 by a comparing circuit 58. If the output signal is lower than the reference voltage 56, a detection signal representing a seating of a person is outputted. By this, irrespective of the mode of sitting the seating can be detected without fail, whereby the toilet seat is heated and cleaning water is flushed out.