PURPOSE: To provide a multiple light branching device which suppresses the occurrence of crosstalk to accurately send an optical signal by forming optical interference films at regular intervals so that adjacent parallel beams are not branched in the same face at the time of arrival of parallel beams at boundaries of glass pillars.

CONSTITUTION: In a multiple light branching device 35 which branches parallel beams, which transmit plural optical signals emitted from a ribbonlike optical fiber by optical interference films, glass pillars 36 to 39 and a protective glass body 40 have dimensions of 1mm thickness, 1mm width, and 4mm length, and optical filters 41 to 44 are formed at intervals of 1mm on respective boundaries of glass prisms 36 to 39 and the protective glass body 40. Parallel beams which transmit two optical signals emitted from the ribbonlike optical fiber are divided into two of transmitted light and reflected light by optical filters 41, and this transmitted light is divided into two of transmitted light and reflected light by optical filters 43. Parallel beams made incident on optical filters 42 and 44 are divided in the same manner, and each reflected light is received by a sensor array.