To provide a vehicle occupant detection device in which a load sensor is minimized by appropriately integrating each function and the device is totally constituted at low cost.

The device is equipped with strain-type load sensors 21 to 24, and the occupant detection ECU10. The strain-type load sensors 21 to 24 output load data in a vehicle seat 5. The occupant detection ECU10 has a CPU which is as an operation part performing determination of an occupant state based on a load data output, a 5 V power source 12 which supplies power source to the CPU11, and a communication I/F 15 which transmits the determination result of the occupant state with the CPU11 to an airbag ECU43. The power source is supplied to the load sensor 21 or the like from the 5 V power source 12 provided on the occupant detection ECU10. Since the power source is integrated into the occupant detection ECU 10 side, the load sensor 21 or the like can be miniaturized and the determination of the occupant state can be precisely performed without being affected by fluctuation of the power supply voltage.