Laser processing method and laser processing apparatus

The purpose of the present invention is to detect that a hole has passed through a glass substrate when the glass substrate is perforated with a laser beam. A laser processing device is provided with:a table on which a substrate to be processed is placed; a laser irradiation system that irradiates the substrate with laser light; and a control unit for controlling each part of the device in orderto perform a machining operation. The control unit detects that the hole has passed through by detecting that the light detection level on the end surface of the substrate has been lowered to a predetermined level during the processing operation. 本发明目的在于，特别是在以激光对玻璃基板开孔的情况，能检测出孔已贯通。解决手段：一种激光加工装置，具有：工作台，载置有须加工的基板；激光照射系统，对该基板照射激光；以及控制部，为了进行加工动作而控制装置各部分；其中，该控制部借由检测出在加工动作时于该基板的端面的光检测位准已降低至预定的位准而检测出孔已贯通。