An impact force is transmitted to a tip end tool due to the changes of the air pressure within an air chamber generated by the reciprocal operation of the piston within a striker. The attachment portion of a tip end tool holding member for holding the tip end tool to a cylinder casing is sandwiched between buffers disposed in the two directions of the axial direction of the tool thereby to elastically support the tip end tool holding member to be movable in the two directions of the axial direction of the tool.