A driver including: an ejection part to which a fastener is supplied; a driver blade which moves from a first position toward a second position and drives the fastener into a driven member; and a rack provided to the driver blade. The driver further includes: a rotary component engaging with the rack and moving the driver blade from the second position to the first position; and a lock plate engaging with the rack. The driver blade moves from the second position to the first position while the rotary component rotates once, the rotary component is released from engaging with the rack after the driver blade moves from the second position to the first position, and moves from the first position to the second position, and the lock plate is engageable with the rack when the driver blade stops before reaching the second position from the first position.