Gel-like material or viscoelastic polymer is placed in a portion having a three-dimensional shape. A power tool driving force transmission mechanism transmits a rotary driving force from a rotary drive source to operate the power tool; and a housing provides an outer shell for the power tool. A tail cover is provided at least a region of the housing, held by an operator; and gel-like material, enclosed by a resin film into a gel pack, is placed between the tale cover and the housing. The tail cover is composed of an elastomer member and a resin member, which is integrally formed with the elastomer member and has a higher hardness than the elastomer member. A portion receiving the gel pack is composed of the elastomer member, and a portion connected to the housing is composed of the resin member. The gel pack may be substituted with viscoelastic polymer.