A light guide includes a core and a clad made of a material having an index of refraction different from an index of refraction of the core and covering the core, in which at least one of a light incident surface or a light exit surface of the core is arranged while shifted in parallel without changing respective inclined angles so that the inclined surface is divided into a plurality of inclined surfaces parallel in a longitudinal direction (X direction) of the rectangular shape in the orthogonal projection and the plurality of inclined surfaces closer to the light emitting portion are positioned in a direction (Z direction) of moving away from the end face to be in a shape extending in the direction (Z direction) of moving away from the end face in a stepwise manner as a whole.