Abstract: A sitting detection system determines whether an occupant is seated in a vehicle seat or not by applying a DC voltage to a sheet-like detection electrode that is provided in the seat, and measuring the time for capacitance between the detection electrode and a ground to be charged to a predetermined level using simple implement. The use of the conductive woven cloth, which is formed with the surface member of the seat, as the detection electrode enables not to degrade the texture of the seat. The threshold time for detecting whether an occupant is seated in a seat or not may be set using a charging time which is measured when no occupant is seated in the seat as the initial value.