Abstract: A tire pressure detector connected to the air valve of a vehicle tire to detect its inside pressure, the detector including a tubular shell fastened to the air valve of the vehicle tire, a transparent top cover fastened to the shell to hold down a socket inside the shell, a valve block moved in the socket subject to the condition of the tire pressure of the vehicle tire, and a display bolt supported on a spring member in the valve block, wherein the air pressure of the vehicle tire passes through the air valve of the vehicle tire and the air holes at the socket to push the valve block upwards in the top cover relative to the display unit upon connection of the shell to the air valve of the vehicle tire, and the air pressure of the vehicle tire is read out by viewing the area of the lower portion and upper portion of the display bolt being blocked by the valve block.