An air tool with a Helmholtz silencer, the air tool comprising: a housing including a motor chamber for accommodating an air motor, an air supply path for supplying compressed air to the motor chamber, and an air discharge path for passing exhaust air from the motor chamber to discharge the exhaust air to an outside from a downstream outlet; and a silencer member provided in the air discharge path along a longitudinal direction of the air discharge path to divide an interior of the air discharge path into a resonance chamber (46, 48) extending along the longitudinal direction of the air discharge path and an air discharge passage extending in the longitudinal direction adjacently to the resonance chamber (46, 48), wherein: the air discharge passage is divided from the resonance chamber (46, 48) to receive exhaust air from the motor chamber and pass the exhaust air to the downstream outlet, and the air discharge passage extends rectilinearly from the downstream outlet upstream toward the motor chamber, and the silencer member has an opening communicating between the air discharge passage and the resonance chamber (46, 48), the opening and the resonance chamber (46, 48) constituting, in combination, a sound-damping chamber using Helmholtz resonance, characterised in that the silencer member is inserted into the air discharge path from the downstream outlet toward an upstream side where the motor chamber is located, thereby dividing the air discharge path into the resonance chamber (46, 48) and the air discharge passage. a housing including a motor chamber for accommodating an air motor, an air supply path for supplying compressed air to the motor chamber, and an air discharge path for passing exhaust air from the motor chamber to discharge the exhaust air to an outside from a downstream outlet; and a silencer member provided in the air discharge path along a longitudinal direction of the air discharge path to divide an interior of the air discharge path into a resonance chamber (46, 48) extending along the longitudinal direction of the air discharge path and an air discharge passage extending in the longitudinal direction adjacently to the resonance chamber (46, 48), wherein: the air discharge passage is divided from the resonance chamber (46, 48) to receive exhaust air from the motor chamber and pass the exhaust air to the downstream outlet, and the air discharge passage extends rectilinearly from the downstream outlet upstream toward the motor chamber, and the silencer member has an opening communicating between the air discharge passage and the resonance chamber (46, 48), the opening and the resonance chamber (46, 48) constituting, in combination, a sound-damping chamber using Helmholtz resonance, characterised in that the silencer member is inserted into the air discharge path from the downstream outlet toward an upstream side where the motor chamber is located, thereby dividing the air discharge path into the resonance chamber (46, 48) and the air discharge passage. the air discharge passage is divided from the resonance chamber (46, 48) to receive exhaust air from the motor chamber and pass the exhaust air to the downstream outlet, and the air discharge passage extends rectilinearly from the downstream outlet upstream toward the motor chamber, and the silencer member has an opening communicating between the air discharge passage and the resonance chamber (46, 48), the opening and the resonance chamber (46, 48) constituting, in combination, a sound-damping chamber using Helmholtz resonance, characterised in that the silencer member is inserted into the air discharge path from the downstream outlet toward an upstream side where the motor chamber is located, thereby dividing the air discharge path into the resonance chamber (46, 48) and the air discharge passage.