A light emitting apparatus includes a light source, a thin plate-shaped mirror unit which guides light from the light source, and a tension imparting means which imparts tension to the mirror unit. The tension imparting means may have at least any one of a first tension imparting mechanism which imparts tension in a first direction toward the light source along a surface of the mirror unit and a second tension imparting mechanism which imparts tension in a second direction opposite to the first direction, and further, the tension imparting mechanism may have at least any one of a third tension imparting mechanism which imparts tension in a third direction in parallel with the light source along the surface of the mirror unit and a fourth tension imparting mechanism which imparts tension in a fourth direction opposite to the third direction.