OCCUPANT SENSOR

To provide an occupant sensor that can reliably judge whether the object loaded on a seat is a child restraint system or an adult even when the child restraint system is fixed by using a seatbelt. The occupant sensor detects whether or not the seatbelt extraction amount sensor (switch) is ON. When the extraction amount sensor is ON, the object loaded on the seat is judged as being a child restraint system or a child. When the seatbelt extraction amount sensor is not ON, the sensor determines whether or not the value of load detected by the seat load sensor is not less than 30 kg. When the load is less than 30 kg, the occupant is judged as being an adult. When the load is less than 30 kg, the occupant is judged as being a child or a child restraint system.