After the running wheels 12FR, 12FL, 12RR and 12RL are replaced from the summer wheel set to the winter wheel set (non-mounted wheels 12), when the vehicle 10 is running at a speed more than a predetermined speed, and if all ID numbers contained in the data received within a predetermined time are entirely identical to the sensor IDs corresponding to the non-mounted wheels 12, the sensor IDs identified in the sensor ID identification portion 54 are automatically switched from the sensor IDs corresponding to the summer wheel set to the sensor IDs of the winter wheel set.