PURPOSE: To reduce the cost for development of a product and to accelerate the speed of working therefor, by forming an angle material of prescribed dimensions by a method wherein an angle material piece having a prescribed section is cut out of a metal material by wire-cut electric discharge machining and a plurality of said pieces are bonded together.

CONSTITUTION: With a maching liquid being poured, a voltage is impressed for discharge on a wire 2 of copper, brass or the like which is passed through one point of a columnar metal material 1 such as a billet of an aluminum alloy, and the wire 2 is moved on the basis of prescribed data to cut the material. A forming material piece 3 thus cut out is heated to a temperature of 500W550°C and then quenched or cooled by air, and is subjected to T5 processing. Thereafter a plurality of said pieces are bonded together by a bonding agent or the like, so as to form a test angle material of a prescribed length. This angle material is assembled, and a required performance test is applied to the assembled material. By applying the wire-cut electric discharge machining, said material can be manufactured more inexpensively than that by extrusion molding, wire feeding can be automated by a numerical control of a computer, and modification of design is also facilitated.