To provide a method for forming a via hole which is manageable in a wider range of an irradiation time and can be easily handled in an actual manufacturing line.

In performing working of copper foil of an upper layer and interlayer insulating layer for forming an interlayer conduction structure of a laminated wiring board by a copper direct method using a laser beam, the pulse height of a laser beam is set slightly higher and the pulse length is determined relatively longer. As a result, the management range of the pulse length can be taken wider. Accordingly, the method of forming the via hole which is wide in the management range and can be easily implemented even for manufacturing facilities for mass production is realized.