The invention discloses a pneumatic punching machine which comprises an air cylinder, an upper die base plate, a lower die base plate, a fixed plate, a positioning seat and a movable supporting rod, wherein the air cylinder comprises a second air cylinder; the second air cylinder and the positioning seat are respectively arranged on the fixed plate; the middle of the movable supporting rod is hinged to the positioning seat; one end of the movable supporting rod is hinged with one end of the upper die base plate; the other end of the movable supporting rod is hinged with one end of a movable block; the other end of the movable block is connected with a piston rod of the second air cylinder; the other end of the upper die base plate is connected with a rivet positioning block; the rivet positioning block is connected with the positioning seat through a sliding block; the sliding block is arranged on the side face of the rivet positioning block; an opening for placing the movable supporting rod is formed on the positioning seat; an adjustment block is arranged at the end part of the opening; one end of an adjustment screw rod penetrates through the adjustment block and then is pressed against the movable supporting block; and a first air cylinder is arranged below the fixed plate. The pneumatic punching machine has the characteristic of simple and rational structure, is operated flexibly, is safe and reliable and can position a workpiece accurately.