The present invention is directed to an assembly of an optical fiber and an optical fiber holder for holding the optical fiber, the optical fiber having an end surface formed at an end portion thereof, the end surface being configured to perform light coupling with a light emitting element or with a light receiving element. The optical fiber holder comprises; a throughhole which extends through the optical fiber holder and a recess that is positioned on a surface of the optical fiber holder and that is provided with an opening of the throughhole. The optical fiber is inserted through the throughhole and an adhesive is filled in a gap between an inner wall of the throughhole and an outer periphery of the optical fiber, the adhesive being used for adhering the optical fiber to the optical fiber holder. The end portion, on which is formed the end surface of the optical fiber, protrudes from the opening and terminates within the recess.