A prism 11 is formed which has a first face 11a opposing an end face of an optical fiber 21 and receiving a light-to-be-received from the optical fiber, second and third faces 11b and 11c adjoining opposite ends of the first face 11a at right angles and opposing each other, a fourth face 11d for reflecting the light-to-be-received from the face 11a toward the face 11b, and a fifth face 11e reflecting a light-to-be-transmitted as projected from a light source through the face 11c toward the face 11a. First and second light-to-be-received converging lenses 12 and 13 are disposed on the faces 11a and 11b of the prism 11 and first and second light-to-be-transmitted converging lenses 14 and 15 are disposed on the faces 11a and 11c. The tilt angles .beta.1 and .beta.2 of the faces 11d and 11e with respect to the optical fiber axis 21a are less than 45.degree.. With this configuration, if the light-to-be-received enters the light-receiving element 22 and the light-emitting element 23 and is reflected by these elements, such reflected light is prevented from returning back into the optical fiber whereby occurrence of far-end crosstalk can be suppressed.