In a hammer drill, a coil spring is disposed rearward of a piston cylinder inside a housing so as to press the piston cylinder to an advanced position when the hammer drill operates in a drill mode, and a supporting plate is disposed at a rear end of the piston cylinder. The supporting plate includes a pair of side plates and a base portion connecting front ends of the side plates. The base portion is in contact with a rear surface of the piston cylinder, and rear ends of the side plates are in contact with a front end of the coil spring. Openings provided in the side plates are configured to hold a pin on which a connecting arm is pivoted.