A screwdriver includes a driver portion, a slider case having a guide slot, a slider (7), comprising parts (7A) and (7B) reciprocating, in the slider case, an arm portion comprising shaft arm (16) and clutch arm that is supported and rotates in the slider (7), engaged with the guide slot of the slider case, and oscillates in accordance with the reciprocation of the slider, and a cylindrical drum that is supported and rotates in the slider, has two flanges (11b) and (11c) engaged with a screw chain belt and a ratchet (11e) engaged with the arm portion, and intermittently delivers the screw chain belt in accordance with the oscillation of the arm portion. The ratchet (11e) of the drum (11) is formed on an inner surface of the flange (11b).