SEAT-OCCUPANCY STATE DETECTION DEVICE

A seat-occupancy state detection device (30) includes: a seat occupancy sensor (21) that forms a pressure sensitive portion (60) on a seat occupancy surface (10) of a seat (1); a load sensor (11) that detects a load applied to the seat occupancy surface; a seat-occupancy state determination unit (71) that determines a seat occupancy state of an occupant on the seat, based on an ON/OFF state of the seat occupancy sensor and the load which is detected by the load sensor; and an abnormality determination unit that determines an occurrence of a first abnormality in which the ON state of the seat occupancy sensor is maintained, in a case where the seat occupancy sensor is in the ON state, and the load, which is detected by the load sensor, is equal to or lower than a first threshold value indicating an unloaded state.