Inspection method of workpiece and inspection apparatus

An inspection method of a workpiece composed of single-crystal silicon manufactured in such a manner that a specific crystal plane is exposed in each of an upper surface and a lower surface, the inspection method comprising:

• a separation layer forming step of forming a separation layer including a modified layer parallel to the upper surface and cracks that extend from the modified layer inside the workpiece through positioning a focal point of a laser beam with a wavelength having transmissibility with respect to the workpiece to a depth equivalent to a thickness of a wafer to be manufactured from the upper surface of the workpiece and executing irradiation with the laser beam while relatively moving the focal point and the workpiece in a processing feed direction;
• an irradiation step of irradiating whole of the upper surface of the workpiece in which the separation layer has been formed with light having such a wavelength as to be transmitted through the workpiece and reflect at the crack of the separation layer after the separation layer forming step is executed;
• a light reception step of receiving reflected light resulting from the irradiation in the irradiation step and reflection by the crack;
• and
• a determination step of determining a state of the separation layer on a basis of intensity of the reflected light received in the light reception step.