1. A lighting device for inspection, comprising:a housing;
four light source units disposed inside the housing;
a light guide plate that guides light emitted from the light source units and that has four end face portions; and
a reflective portion that is formed on an upper face of the light guide plate and that reflects light toward a lower face of the light guide plate,
wherein one wiring cable is provided for each of the four light source units, and each of the light source units is disposed for each of the end face portions, is able to emit light to each of the end face portions, and is independently controlled through the wiring cable for dimming, and
the four light source units configured such that (1) each of the four light source units emits a single color of light different from colors of light emitted by others of the four light source units, (2) the four light source units can collectively emit a color of light either by switching between ones of the four light source units or by additive color mixing of the different colors, and (3) two or more different colors of light are used sequentially during a single inspection of an inspected article.