A tire air pressure surveillance system is provided with plural air pressure detecting devices disposed in plural tires respectively for detecting air pressure therein and for sending detected results by radio, a receiving device for receiving the detected results from the air pressure detecting devices by radio, and a monitor device for monitoring air pressure in the tires based on the detected results received by the receiving device. The air pressure detecting devices send sensor ID along with the detected results for distinguishing each air pressure detecting device. The sensor ID beforehand memorized in EEPRROM of the monitor device as determination sensor ID is broadcast-sent to the receiving device through a local area network at a predetermined interval. Only the detected results along with the sensor ID corresponding to the determination sensor ID are sent to the monitor device by the receiving device.