To solve the problem of the conventional optical code multiplex transmission system that causes increase in the scale of hardware.

The optical code multiplex transmission system consists of a transmission section, that has a 1st light intensity modulator that modulates a light of a light source with transmission data and a 2nd light intensity modulator that modulates an output of the 1st light intensity modulator with a spread code, at a modulation speed faster than the modulation speed of the output of the 1st light intensity modulator, and of a reception section having a light intensity modulator that receives the arrived optical signal, modulates the optical signal with the same spread code as that used by the 2nd light intensity modulator at the transmitter side and extracts the data modulation signal.