The present invention provides an apparatus for shooting a nail comprising a barrel (1), a barrel support (4), a centering sleeve (6), a link frame (8), a cylinder (9), a piston rod (10) and an outer housing (11), wherein the barrel (1) is mounted removably in the barrel support (4). As desired, the barrel may be removed conveniently to facilitate the replacement of the barrel for different application or removal of the nail blocked in the apparatus for shooting a nail. Furthermore, at least two longitudinally elongated slots may be formed in the centering sleeve and penetrate through the wall of the centering sleeve, the steel balls received in the slots are held in the slots via a snap ring so as to embrace the rod body of the piston rod. Therefore, it is ensured that the piston rod is concentric with the barrel when hitting the nail and the hit force of the piston rod will not lose.