the car body or door can be prevented and improved application_number US 67533208 A description the best mode for carrying out the present invention is described below referring attached drawings fig1 shows an impact wrench 1 as a fastening tool fastening a fastening member such as a bolt to a fastened member such as a nut including a socket 6 for gripping the fastening member a body 2 for supporting the socket 6 rotatably via a rotating shaft 5 and a grip 3 extending from the body 2 for the operator to hold the wrench 1 the body 2 has a motor connected to the shaft 5 for driving the socket 6 and the grip 3 has a trigger 7 for switching the drive of the motor in the wrench 1 the rotating axis of the socket 6 that is the axis of the shaft 5 is the same as the longitudinal direction left and right direction in fig1 of the body 2 the outer periphery of the body 2 is covered with a body cover 11 from the side of the socket 6 head portion to the side of the grip 3 base portion as shown in fig2 the cover 11 is stuck to the body 2 at the middle 11 b and the base end 11 c whereby the sealing is secured between the body 2 and the cover 11 the cover 11 extends the leading end 11 a from the body 2 toward the socket 6 covering the surroundings of the shaft 5 with defining a.