To efficiently sort and collect specified parts and members in a recycling process in which various waste electric appliances are treated at random.

In a cutting method, the output state of laser beam 3 is detected when outputting the laser beam 3 to a workpiece, and a reference value is established, which determines based on the result of detection whether or not the output state of the laser beam 3 is in a normal operational range. When the result of detection exceeds the reference value, the output state of the laser beam 3 is determined to be abnormal, and the output of the laser beam 3 is controlled to stop or guided in a normal operational range.