PURPOSE: To form both a sinking part and a bulging part on a top plate of can at the same time, by providing a recessing part to the upper surface of a hard rubber die and a projecting part to the lower surface of a plunger sunch in a can opening processing device.

CONSTITUTION: A top plate 27 of can is mounted on a holder 15 to concentrically position a projecting part 27a of the plate 27 onto a hard rubber die 14. Next, a segmental die 18 is lowered from the upper side to fitly insert the inner wall 19a of an upper die 19 to the slant surface of the outer wall 18a of the die 18, thereby the die is clamped to have a prescribed diameter and the holder 15 is simultaneously pressed till it touches at a lower die 13. At the same time, a plunger punch 20 is also lowered, and the upper surface of a projecting part 27a of the plate 27 is pressed downward by a projecting part 20a of the die 20 to draw a sinking part 27a. Next, the die 20 is further lowered to press the die 14, and then, the upper peripheral edge of the die 14 is bulged outward to form a bulging part 27d of the plate 27, thereby the part 27a of the plate 27 is deformed so as to conform to the shapes of the 20 and the die 18.