A tire mounting state detection system for detecting the state of a transmitter equipped on a tire mounted on a vehicle, including a receiving unit disposed in the vehicle for receiving a radio signal transmitted from the transmitter; and the tire mounting state detection system comprising: a vehicle configuration holding unit for holding a vehicle configuration including the number of wheels of the vehicle; a transmitter number detection unit for detecting the number of transmitters based on the radio signal received by the receiving unit; a state detection unit for detecting whether or not the number of transmitters exceeds or is short of the number of wheels, based on the number of wheels based on the vehicle configuration held by the vehicle configuration holding unit and the number of transmitters detected by the transmitter number detection unit; an output unit for outputting that the state of the transmitter is abnormal when the state detection unit determines that the number of the transmitters exceeds or is short for the number of the wheels, characterized in that the receiving unit includes a first receiver and a second receiver, the second receiver is disposed at a position different from the first receiver in the vehicle width direction, the first receiver and the second receiver are disposed closer to the front wheels of the vehicle or closer to the rear wheels of the vehicle, and the tire mounting state detection system comprising: a first measurement unit for measuring the first signal strength, which is the strength of the radio signal received by the first receiver, for each transmitter; a second measurement unit for measuring the second signal strength, which is the strength of the radio signal received by the second receiver, for each transmitter; and a calculation unit for calculating an overall strength of the radio signal for each transmitter by using the first signal strength and the second signal strength; wherein, the state detection unit detects, based on a magnitude relationship of the overall strength, that a tire in which the number of transmitters exceeds or a tire in which the transmitter is not activated is mounted at a wheel position on either the front wheel side of the vehicle or the rear wheel side of the vehicle. a vehicle configuration holding unit for holding a vehicle configuration including the number of wheels of the vehicle; a transmitter number detection unit for detecting the number of transmitters based on the radio signal received by the receiving unit; a state detection unit for detecting whether or not the number of transmitters exceeds or is short of the number of wheels, based on the number of wheels based on the vehicle configuration held by the vehicle configuration holding unit and the number of transmitters detected by the transmitter number detection unit; an output unit for outputting that the state of the transmitter is abnormal when the state detection unit determines that the number of the transmitters exceeds or is short for the number of the wheels, characterized in that the receiving unit includes a first receiver and a second receiver, the second receiver is disposed at a position different from the first receiver in the vehicle width direction, the first receiver and the second receiver are disposed closer to the front wheels of the vehicle or closer to the rear wheels of the vehicle, and the tire mounting state detection system comprising: a first measurement unit for measuring the first signal strength, which is the strength of the radio signal received by the first receiver, for each transmitter; a second measurement unit for measuring the second signal strength, which is the strength of the radio signal received by the second receiver, for each transmitter; and a calculation unit for calculating an overall strength of the radio signal for each transmitter by using the first signal strength and the second signal strength; wherein, the state detection unit detects, based on a magnitude relationship of the overall strength, that a tire in which the number of transmitters exceeds or a tire in which the transmitter is not activated is mounted at a wheel position on either the front wheel side of the vehicle or the rear wheel side of the vehicle. a first measurement unit for measuring the first signal strength, which is the strength of the radio signal received by the first receiver, for each transmitter; a second measurement unit for measuring the second signal strength, which is the strength of the radio signal received by the second receiver, for each transmitter; and a calculation unit for calculating an overall strength of the radio signal for each transmitter by using the first signal strength and the second signal strength; wherein, the state detection unit detects, based on a magnitude relationship of the overall strength, that a tire in which the number of transmitters exceeds or a tire in which the transmitter is not activated is mounted at a wheel position on either the front wheel side of the vehicle or the rear wheel side of the vehicle.