A tire mounting position detection system (100, 100 A) for detecting at which wheel position (1 to 6) of a vehicle each tire (31 to 36) equipped with a transmitter (41 to 46) is mounted, including a receiving unit disposed in the vehicle and for receiving a radio signal transmitted from the transmitter (41 to 46); wherein: the receiving unit includes: a first receiver; and a second receiver disposed at a position different from the first receiver in the vehicle longitudinal direction and the vehicle width direction; and the tire mounting position detection system (100, 100 A) comprising: a first measurement unit for measuring a first signal strength (R1 (x)), which is strength of the radio signal received by the first receiver, for each transmitter (41 to 46); and a second measurement unit for measuring a second signal strength (R2 (x)), which is strength of the radio signal received by the second receiver, for each transmitter (41 to 46); characterized in that the tire mounting position detection system (100, 100 A) comprises: a calculation unit for calculating an strength ratio, which is a ratio using the first signal strength (R1 (x)) and the second signal strength (R2 (x)), for each transmitter (41 to 46); and a position detection unit for detecting a wheel position (1 to 6) on which a tire (31 to 36) equipped with the transmitter (41 to 46) is mounted, based on the first signal strength (R1 (x)), the second signal strength (R2 (x)), and the strength ratio for each transmitter (41 to 46). a first receiver; and a second receiver disposed at a position different from the first receiver in the vehicle longitudinal direction and the vehicle width direction; and the tire mounting position detection system (100, 100 A) comprising: a first measurement unit for measuring a first signal strength (R1 (x)), which is strength of the radio signal received by the first receiver, for each transmitter (41 to 46); and a second measurement unit for measuring a second signal strength (R2 (x)), which is strength of the radio signal received by the second receiver, for each transmitter (41 to 46); characterized in that the tire mounting position detection system (100, 100 A) comprises: a calculation unit for calculating an strength ratio, which is a ratio using the first signal strength (R1 (x)) and the second signal strength (R2 (x)), for each transmitter (41 to 46); and a position detection unit for detecting a wheel position (1 to 6) on which a tire (31 to 36) equipped with the transmitter (41 to 46) is mounted, based on the first signal strength (R1 (x)), the second signal strength (R2 (x)), and the strength ratio for each transmitter (41 to 46). a first measurement unit for measuring a first signal strength (R1 (x)), which is strength of the radio signal received by the first receiver, for each transmitter (41 to 46); and a second measurement unit for measuring a second signal strength (R2 (x)), which is strength of the radio signal received by the second receiver, for each transmitter (41 to 46); characterized in that the tire mounting position detection system (100, 100 A) comprises: a calculation unit for calculating an strength ratio, which is a ratio using the first signal strength (R1 (x)) and the second signal strength (R2 (x)), for each transmitter (41 to 46); and a position detection unit for detecting a wheel position (1 to 6) on which a tire (31 to 36) equipped with the transmitter (41 to 46) is mounted, based on the first signal strength (R1 (x)), the second signal strength (R2 (x)), and the strength ratio for each transmitter (41 to 46). a calculation unit for calculating an strength ratio, which is a ratio using the first signal strength (R1 (x)) and the second signal strength (R2 (x)), for each transmitter (41 to 46); and a position detection unit for detecting a wheel position (1 to 6) on which a tire (31 to 36) equipped with the transmitter (41 to 46) is mounted, based on the first signal strength (R1 (x)), the second signal strength (R2 (x)), and the strength ratio for each transmitter (41 to 46).