PURPOSE: To provide a method for working a pinhole and a circular hole or the like in a curved surface body such as a tube stock.

CONSTITUTION: An upper fixing jig 8 and a lower fixing jig 9 respectively having jig grooves 8', 9' having the diameter coinciding with the outer diameter of a tube stock to be worked in each inner part of a pair of nearly square shaped metal regulus members, a die hole 10' penetrating with duplication a part of the circumference of the jig grooves 8', 9' in the inner surface side of the upper fixing jig 8 and the lower fixing jig 9, a die 10 reciprocating in the die hole 10' and a connecting means such as a hinge 11 for connecting the upper fixing jig 8 to the lower fixing jig 9 at one side are arranged, and the moving path of the die 10 passes through the inside of a part of the circumference of the jig grooves 8', 9'.