To provide a laser machining method for uniformly laser-punching a plurality of via holes for IVH without depending on thickness of a workpiece in a laser punching part, a density degree of fiber such as glass cloth, resin material quality, and laser intensity; and to provide a laser device used for the method.

In the laser punching method of the via hole for IVH, wherein layers of a multilayer printed wiring board are connected, for solving the problem, the laser punching method of the printed wiring board senses a change of combustion light obtained by burning and dissolving the workpiece by laser irradiation light when it reaches a circuit conductor of an inner layer, and decides number of additional shot times of laser machining of an identical part. The laser device is provided with a judgement sensor sensing the change of combustion light when the laser irradiation light burns and dissolves the workpiece.