FASTENING TOOL

The fastening tool includes a housing, a trigger, a cylinder, a piston, and a main valve. The main valve allows a communication between the cylinder and the first air chamber in conjunction with an operation of the trigger. The housing is formed with a first air chamber, a second air chamber, and a third air chamber. The second air chamber is communicated with the cylinder in conjunction with a movement of the piston. The third air chamber accumulates or discharges the compressed air in the first air chamber in conjunction with the operation of the trigger. The cylinder is movable between a first position where the cylinder upper chamber being in communication with the first air chamber, and a second position where the cylinder upper chamber being blocked from the first air chamber based on a differential pressure between the second air chamber and the third air chamber.