A pneumatic motor includes a housing, a rotor, an air flowing unit and an air-supply unit. The housing has an inside space formed along an axis and divided sequentially into a rotor chamber, a valve chamber and an inlet chamber. The rotor is rotatably mounted in the rotor chamber. The pneumatic valve is mounted in the rotor chamber and the valve chamber and includes an air flowing unit and an adjusting gate. The air-supply unit is mounted in the inlet chamber and is connected to a source of compressed air, so the compressed air can flow from the inlet chamber into the valve chamber and then flow through the pneumatic valve to drive the rotor.