Abstract: A silencer mechanism for an impact wrench can reduce noise of exhaust and increase, rather than decrease, power of an impact wrench. The silencer mechanism comprises a silencer element inserted in an exhaust passage, and an outlet pipe for holding in place the silencer element. The silencer element has larger-diameter tubular portions located at both ends thereof and a smaller-diameter tubular portion located between the larger-diameter tubular portions. A plurality of holes each having a first diameter are formed in the larger-diameter tubular portion located closer to an exhaust inlet such that the holes are equally spaced in the circumferential direction, while a plurality of holes each having a second diameter are formed in the larger-diameter tubular portion located closer to an air outlet such that the holes are equally spaced in the circumferential direction. The outlet pipe is screwed into the exhaust passage so as to hold in place the silencer element inserted in the exhaust passage.