To provide an optical coupler which includes an anamorphic lens in order to improve the coupling efficiency between a laser and an optical fiber.

An optical coupler 16 is provided with an object focusing means 18, which focuses a divergent elliptic beam emitted from a laser source 12 to a convergent elliptic beam propagated toward an optical fiber 14, and an anamorphic lens 20 which is arranged at the output point of the object focusing means 18 and is adapted to convergence in a first part propagated along the axis of a high speed to convert the elliptic beam to an approximately annular beam and increases convergence in a second part propagated along the axis of a low speed thereafter so that the annular beam is coupled to the optical fiber.