TIRE AIR PRESSURE MONITORING DEVICE

A tire air pressure monitor device provided for monitoring the air pressure in tires is provided with a pressure sensor 2a installed in the tire of each of the wheels 1 for detecting the air pressure in the tire; a transmitter 2d provided on each of the wheels 1 for transmitting by wireless signals the air pressure information along with a sensor ID when at a predetermined rotation position; a receiver 3 provided on the vehicle body for receiving the wireless signals; a wheel speed sensor 8 provided on the vehicle body to correspond to each of the wheels 1 for determining the rotation position of the wheel 1; and a TPMSCU 4 for acquiring the rotation position of the wheels ten or more times when a wireless signal containing a certain sensor ID is transmitted, accumulating the same as rotation position data for the wheels 1, and determining the wheel position corresponding to the rotation position data having the smallest degree of dispersion from among each of the rotation position data as the wheel position for the transmitter 2d corresponding to the sensor ID.