To perform miniaturization, to lower a price and to perform highly reliable optical communication by providing an arithmetic part for eliminating a signal leakage interference part from the optical signals of transmission to the optical signals of reception in the optical transmitter-receiver of a single core two-way optical communication channel.

The optical signals L1 of a light emission part 12 are reflected vertically upwards at the semi-transmissive mirror 141 of an optical element 14, led to an optical fiber and transmitted, reception signals L2 are obliquely transmitted at the mirror 141 and made incident on a light reception part 23 and a part of the signals L1 is also leaked to the light reception part 23 as stray light. The light reception part 23 is provided with cells 231 and 232 for bisecting and receiving the signals L2 and the stray light and the detection current is computed in the arithmetic part 26 provided with current/voltage conversion circuits 261 and 262 and a differential amplifier circuit 263. The arithmetic part 26 electrically offsets the stray light by the adjustment of transimpedance and gain and eliminates the signal leakage interference part and the highly reliable optical communication is made possible.