PURPOSE:To obtain a die set of a comparatively simple structure, and to work quickly a counter sink, etc. by forming a punch by a double structure consisting of the first and the second punches, and providing a means for cooperating both the punches. CONSTITUTION:When a punch head 11 of a punch 3 descends, its tapered surface 11c presses a counter-sunk punch 7 through a steel ball 17, and an edge part 7f of the counter-sunk punch 7 contacts a plate material 21. At the initial stage of working, an edge part 6b of a punch 6 stands on the same plane as the edge part 7f, and a counter-sunk part 22a is worked. When the steel ball 17 reaches a position opposed to an annular groove 14, the steel ball 17 is pushed into the annular groove 14 by the tapered surface 11c. In this state, the edge part 6b of the punch 6 is separated from a pressing force, projects and advances from the edge part f, and a hole part 22b is worked on the plate material 21.