A nail gun has a free end 19a and central potion of a trigger arm 19 positioned within a trigger 11, on an upper end 12a of a safety portion 12 and at a plunger 17, respectively. When the trigger 11 is pivoted on its pivot end 16, pivoting movement of the trigger 11 moves a pivot end 18 of the trigger arm 19 to press the central portion of the trigger arm 19 into contact with the plunger 17 and, with the plunger 17 serving as a fulcrum, to press the free end 19a downward against the upper end 12a of the safety portion 12. If downward movement of the safety portion 12 is obstructed when the trigger 11 is pivoted, the upper end 12a contacted by the free end 19a of the trigger arm 19 serves as a fulcrum around which the trigger arm 19 pivots with movement of the trigger 11, whereupon the central portion of the trigger arm 19 presses the plunger 17 inward so that an activation switch 10 activates a blade 7 to eject a nail through a nose piece 5.