PURPOSE: To obtain the function of an optical multi-socket which connects plural terminals mutually by arranging four half-mirrors in a housing at respective vertexes of a rectangle, and reflecting and transmitting a light signal which is incident at 45° by and through the four half-mirros and projecting it out of the housing.

CONSTITUTION: Light O1 incident to the housing 1 from a lens R1 has a 45° angle of incidence and is split into two, and this reflected light O2 is projected out of the housing 1 from a lens R5. Transmitted light O3, on the other hand, is incident to a mirror M2 at 45° and split into two, and its transmitted light O4 is projected out of the housing 1 from a lens R4. The reflected light O5, on the other hand, is incident to a mirror M3 at 45° and split into two. The transmitted light O6 is projected out of the housing 1 from a lens R7 and its reflected light O7 is incident to a mirror M4 and split into two. Its transmitted light O8 is projected out of the housing 1 from a lens R3. Thus, the light O1 incident from the one lens R1 is reflected by and transmitted through the half-mirrors M1W M4 repeatedly to output projection light beams O2, O4, O6, and O8 from all the projection light lenses R5WR8.