Disclosed herein is an optical interconnecting system for transmitting a large amount of data. The system includes a bidirectional transmitting/receiving circuit that is installed at each of both ends of a data line between chips or boards, selectively receives an electric signal or an optical signal, amplifies and converts the received signal and selectively outputs the signal. The optical interconnecting system integrates a transmitter and a receiver into one bidirectional transmitting/receiving circuit to reduce circuit design and manufacturing costs and decrease power consumption. The system can integrate the bidirectional transmitting/receiving circuit in a highly integrated semiconductor chip and extend it to a multi-dimension multi-channel form to produce a compact package. Moreover, the system can freely select an electric signal or an optical signal as input/output signal forms at input/output stages using the select switches of the bidirectional transmitting/receiving circuit and thus the system can be applied to various applications.