PURPOSE: To produce a product having high dimensional accuracy at a good yield by providing a circular conical or V-notch-shaped projection to the top end of a thin sheet-shaped punch having the top end part formed to an approximately V shape and bending the product by such punch.

CONSTITUTION: The circular conical or V-notch-shaped projection 5 is provided to the top end of the thin sheet-shaped punch 4 having the top end part formed to the approximately V-shape to form the punch for working the edge bend. The part of the working member formed to a rectangular strip shape is set at the alternate long and two short dashes line above the approximately V-shaped fine groove 3 formed to a die 2 and while the thickness is restrained in the groove 3 along the surface of the working member, the punch 4 is lowered to bend the working member by biting the projection 5 to the top end face of said member. The working member is thus bent in the prescribed position without moving the member to the right and left and the product 1 having the high dimensional accuracy is obtd.