There is disclosed a light guide for guiding light from a light source in a longitudinal direction and radiating the light to illuminate an object to be illuminated, which includes a diffuser for diffusing the light from the light source along the longitudinal direction of the light guide, and a radiator for radiating the light diffused by the diffuser in a predetermined direction. By arranging the diffuser and the radiator so that a normal line passing through the center of the width of the diffuser is different from the predetermined direction at least in the vicinity of the light source when viewed in the longitudinal direction of the light guide, the illuminance distribution of the longitudinal direction of the light guide is uniformed.