PURPOSE: To send light radiated from a light emitting element to a light receiving element at a high efficiency by providing clear, translucent optical guide layers on the top surfaces of the light emitting and light receiving elements.

CONSTITUTION: A pair of a light emitting element 13 and a light receiving element 14 are located closely to each other on the upper surface of a bottom member of an insulated recessed case 20 with the respective bottom electrodes being connected to conductor wiring (1-1) and (1-2). The recessed space inside the recessed portion of the insulated recessed case 20 and a pair of the light emitting element 13 and the light receiving element 14 are filled up with a translucent sealing layer. A light shielding body 10 having a light shielding cap on a reflecting surface 9 at the side of the translucent guide plate 24 is provided at the top of an opening of the insulated recessed case 20. By doing this, a light radiated at a high efficiency from the light emitting element can be incident to the light receiving element at a high efficiency.