A tire pressure detector disposed at a wheel, wherein the wheel includes a rim and a tire mounted around the rim, with a pressure space formed between the tire and the rim. The rim includes an air tap connected with the pressure space. The tire pressure detector includes a main body movably disposed in the pressure space and provided with a housing space, and a detection module disposed in the housing space. The detection module further includes a sensing unit for sensing the air pressure in the pressure space and producing a pressure signal. A central processing unit of the detection module receives the pressure signal and wirelessly transmits the pressure signal through the wireless transmission unit. Therefore, vibration and waving issue due to imbalance weight is avoided, thus balancing the wheel.