An optical coupling apparatus having a temperature control element on which a semiconductor light emitting element, a substrate and a lens are mounted, the semiconductor light emitting element being mounted on the substrate, and rays of light from the semiconductor light emitting element being introduced into the lens. A base on which the temperature control element is disposed, a through-hole portion formed in a housing wall portion installed on the base, penetrating through the housing wall portion and having a wall surface portion longer than a thickness of the housing wall portion and an optical fiber communicated with the through-hole portion and receiving converted light from the lens introduced thereto. A length of the substrate in a direction connecting the light emitting element to the optical fiber is within a range from 0.1 to 0.25 with respect to a length of the base sandwiched by the housing walls of the substrate.