Electrodes 2, 3 are contact with an uppermost work W1 and energized with electricity so as to thermally expand an electrode contact portion of the work W1 or alternatively so as to thermally expand the electrode contact portion of the work W1 and a heat transfer portion of an adjoining work W2 to which heat is transferred from the electrode contact portion, and then the portions are contracted so as to form a deformed portion Q and the deformed portion Q is separated from the adjoining works W1, W2 and a gap H is formed between the works W1, W2 which are overlapped, and a laser beam L is irradiated at a position where the gap H is large enough to spread the vapor generated by the vaporization of the coating heated.