To detect easily the edge of a hologram and to inspect very easily whether the hologram is attached within its allowable range.

In the position inspecting method, a transparent plate 2 is set to a reference position and a hologram 1 is placed on the outside of it. Diffraction light is radiated between the maximum contour and the minimum contour of the allowable range for the reference position on which the hologram 1 must be placed. On the inside of the transparent plate 2 two materials are set: an inspection hologram 52 through which visible radiation in the diffraction light is diffracted, and on the inside of it, an inspection plate 5 made of a douser or a translucent plate on the reference position. By using the diffraction light through the hologram 1, or removing the diffraction light through the hologram 1 from the diffraction light through the inspection hologram, it is determined whether the hologram 1 is placed on the prescribed position.