In an electric hammer, ridges are provided in an outer surface of a barrel, grooves are provided in an inner surface of a front cover, and rotation of the front cover with respect to the barrel is prevented by fitting the ridges in the grooves. A flange, which is latched on a stepped portion provided in front of the ridges and the grooves in the inner surface of the front cover, is provided in a peripheral edge of a lock ring, and forward movement of the front cover is restricted by latching the flange on the stepped portion.