Abstract: A device for coupling a laser beam to an end surface of an optical fiber comprises a beam converging lens, a holder for the fiber, a block of a solid material, and a mass of a binder between the block and the end surface and between the block and the holder. The lens and the holder are fixed to each other so as to make the laser beam focus on the end surface. Use is preferred of an arrangement comprising a first and a second holder in which the holders have axial lines, respectively, and hold a laser element for the laser beam and the lens with a beam axis of the laser beam and an optical axis of the lens rendered coincident with the respective axial lines and in which the holders are fixed to each other with the axial lines aligned. The arrangement is effective also in coupling the laser beam to a general transmission medium. Instead of using the arrangement, a lens holder may be fixed to the fiber holder and then to a laser element holder so as to make the laser beam focus on the optical fiber end surface.