PURPOSE: To easily inspect the component with high precision by irradiating the component to be inspected with the light of the light guide almost uniformly over a wide range.

CONSTITUTION: The light guide 10 has a ring-shaped light guide body 12 and optical fibers 14 and 14' which are arranged in the light guide body 12 and guide light from a light source. The light guide body 12 has internal and external annular irradiation openings 20A and 20B, and the light irradiation ends 14a and 14'a of the optical fibers 14 and 14' face the internal and external annular irradiation openings 20A and 20B to irradiate them with the light 18. A cylindrical reflecting plate 26 is provided between the internal and external annular irradiation openings 20A and 20B. This cylindrical reflecting plate 26 reflects the irradiating light 18, with which the plate 26 is irradiated from the light irradiation ends 14a and 14'a through the internal and external annular irradiation openings 20A and 20B, to below the center of the ring of the light guide 10 and below nearby the outer periphery to uniformly irradiate an object surface.