PURPOSE: To perform a forming with a small load by irradiating with a laser beam a part properly surrounded with a slit formed on a plate-like work by a laser beam machining, and heating and deforming the irradiated part while this irradiation heat is held.

CONSTITUTION: A formed work piece 41A is a product manufactured by squeezing with a gradient. Plural T-shaped slits 43 are worked on a work W by the laser beam of a laser beam machine. Irradiated parts 45 which are hatched parts, are heated by being irradiated with a laser beam. Since the heat applied to the work W, does not conduct to surroundings across a line cut by the slit 43, the irradiation heat stops in the irradiated part 45. The work W which became easy to plastically deform by this heat, is pressurized by a die D1 with a recessed shape, provided on a die and left blade 37, and a punch P1 with a projecting shape, provided on a right blade 39 to perform a forming work, and to work a formed work piece 41A. Consequently, a device is made compact, and vibrations and noises are reduced.