Sitting sensor for vehicle

A sitting sensor (1) for detecting a sitting on a seat (5) of a vehicle is provided with a positive conductive wire (15), a negative conductive wire (16), and a switch group including a plurality of switches (S1-S6), which are distributed on a sitting surface of the seat (5) and become ON/OFF responding to a sitting load on the sitting surface. The switches (S1-S6) are supplied with power through the positive conductive wire (15) and the negative conductive wire (16). At least one of the switches (S1-S6) is connected with at least one of the other switches (S1-S6) in series. Accordingly, the sitting sensor (1) can detect the sitting with a high reliability. As alternative, there may be provided at least two positive or negative conductive wires, leading in practice to more than one detecting system in the seat.