To surely discriminate a mounted nondefective and a mounted defective and to surely discriminate whether a different component is mixed or not by a method wherein a conveyed component is endowed with a light emitting property, the component is irradiated with ultraviolet rays and the emitted light of the component is detected by a light receiving element in an inspection process.

As a method in which a resin component such as an engineering plastic component or the like is provided with a light emitting property, an inorganic fluorescent pigment, an organic fluorescent pigment and a fluorescent dye are mixed with a material in advance when the component is manufactured, and their mixture is molded as they are. For example, 1 to 2 wt.% of a fluorescent pigment is added to an epoxy-based adhesive so as to be dispersed, and an adhesive which is endowed with a light emitting property is obtained. A metal plate is coated with the adhesive by using a stamp, and a coating state is inspected. The adhesive which is endowed with the light emitting property is used as an adhesive. In an inspection process, emitted light is captured in a dark place by using a light receiving element, a coating state is observed while ultraviolet rays are being emitted by using a black light in a dark place, and a component is inspected. As a result, whether the component is coated with the adhesive or not can be detected with good contrast (as compared with a case in which the component is not coated with the adhesive).