A nail gun includes a muzzle device, a cartridge device and a driving device. The muzzle device includes a safety member having an abutment end retractable when pushed. The cartridge device includes a stop member for blocking the drive stroke when a number of the nails is less than a predetermined number. The driving device includes a linking member co-movable with the safety member, and a trigger unit including a pivotable trigger, an inner arm co-movable with the trigger, and a switch member. When the switch member is at a sequential striking position and when the trigger is pivoted before a rearward movement of the linking member, the inner arm is withdrawn from a route of the rearward movement to avoid actuation of the drive stroke.