A headlight apparatus includes a high beam headlight and a low beam headlight, which includes: an LED; an LED collimator that is a light source condensing optical system configured to condense a light emitted from the LED; a light guide that is a light distribution controlling light guide, a light from the LED collimator entering the light guide; and a projector lens that a light from the light guide enters, the projector lens being configured to project a light. The light guide includes an incident surface, a plurality of total reflection surfaces, and an emission surface. A first light of an incident light from the incident surface is emitted from the emission surface without reaching the plurality of total reflection surfaces, and a second light of the incident light is emitted from the emission surface via multiple times of total reflection by the plurality of total reflection surfaces.