To provide a tire pneumatic pressure monitoring device capable of enhancing reliability of the tire identification code registration corresponding to each position of four wheels while eliminating troubles of delicately setting the tire pneumatic pressure even upon tire replacement or rotation.

In the tire pneumatic pressure monitoring device comprising tire pneumatic pressure sensors A, B, C and D respectively fitted to tires 1, 2, 3 and 4, reception means fitted to a vehicle side, and a tire identification code registration means to register IDs, the reception means are tuners (1), (2), (3) and (4) with antennas of the number of tires set in a vicinity of each of a plurality of tires 1, 2, 3 and 4. The tire identification code registration means compares the intensity of the radio waves simultaneously received together with the ID when a plurality of IDs are received by the tuners (1), (2), (3) and (4) with antennas, and registers the ID received by the tuner with antenna with the highest intensity of the radio waves.

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