Provided is a technique for easily checking the presence of forsterite without destroying a measurement object. The location where forsterite is present is checked in a region from which light excited by an electron beam is emitted when a material containing forsterite is irradiated with an electron beam. The present invention is preferably applied to the case where the material is a grain oriented electrical steel sheet having a forsterite layer. In addition, it is preferable that the accelerating voltage be 30 kV or more when an electron beam is radiated in the case where the material is a grain oriented electrical steel sheet having a tension coating layer on the forsterite layer.
