To embody an optical crossbar which is small in delay and small in calorific value as well and is producible at a relatively low cost.

The arrays of optical transmission paths 11-1 formed with wedge-like grooves 110 and the arrays of optical transmission paths 11-2 are disposed in such a manner that the wedge-like grooves 110 face to each other between the optical transmission paths 11-1, 11-2 in the direction where these paths intersect orthogonally with each other. The light signals 13 propagated in the optical transmission paths 11-1 are partly reflected as light signals downward at the slopes 112 of the grooves 110 at every passage through the grooves 110. These signals are made incident on the corresponding grooves 110 of the optical transmission paths 11-2 and the course thereof is changed by the slopes 112 of the grooves 110 and these signals are propagated in the optical transmission paths 11-2. At this time, the offset light is selectively applied to the corresponding grooves 110 of the optical transmission paths 11-2 to be connected, is superposed on the light signals and is propagated by the optical transmission paths 11-2. Only the light signals of a specified quantity or above, i.e., only the light signals superposed with the offset light are received as data by the light signal detecting circuit in the output ends 114 of the respective optical transmission paths 11-2.