To smoothly perform stage switching operation by aligning the tip projection of a punch member with a working position marked on a work surface, striking the head of the punch member to carve a center hole in a working position, and performing perforation to the center hole.

On a work surface W where previously right-angled marking-off lines A are drawn, a work abutting surface of a guide main body 2 held by a worker's hands M is allowed to abut on the work surface W, and each vertex 7a formed in the center aligning part 4 is located to position on the marking-off lines A. With the guide main body 2 held, the head 1a of a punch member is struck by a hammer 18, the tip projection 1b is moved vertically to the work surface W, and a center hole is carved in the perforating center position. Further, perforation is performed to the center hole by a twist drill or the like. Thus, the manhour for perforation can be reduced and stage switching can be smoothly done.