Tire position determination system

Each tire pressure detector (4) detects a characteristic point in a detection signal of an acceleration sensor (10) indicating that the tire pressure detector (4) is located at a certain rotation position. When detecting the characteristic point, the tire pressure detector (4) transmits a notification signal (Spk) including the detector ID. Whenever a receiver (12) receives a notification signal (Spk), the receiver (12) acquires an axle rotation amount (C) of a representative wheel (26) and stores the axle rotation amount (C) in a memory in association with the detector ID in the notification signal (Spk). After acquiring axle rotation amounts (C1-C4) associated with the detector IDs of all of the tire pressure detectors (4), the receiver (12) determines mounting positions of tires (2) from the angle each tire pressure detector rotated and the angle each axle (18) rotated between a first determination timing (t1) and a second determination timing (t1).