Car-seat-occupant sensing device

The object of the present invention is to provide a seat-occupant sensing device for a car seat, such that a heater can be installed in the seat without deterioration of sitting comfort. A load sensor (50) is mounted to a cushion frame (21) of a car seat. The end of a flexible cushion support (25) is linked with the load sensor (50). Because the flexible cushion support flexes when a person sits on the seat, the load sensor senses when the person sits on the seat.