A debugging system using optical transmission comprises a sending side and a receiving side. The sending side comprises a debugging-data-generation unit, a modulation unit, and an optical-transmission apparatus. The debugging-data-generation unit generates debugging data according to an operation of the sending side. The modulation unit modulates the debugging data to generate a modulation signal. The optical-transmission apparatus coupled to the modulation unit converts the modulation signal into a first light and transmits the first light. The receiving side comprises an optical-receiving apparatus, a demodulation unit and a data storage device. The optical-receiving apparatus receives the first light and converts the first light into the modulation signal. The demodulation unit is coupled to the optical-receiving apparatus and demodulates the modulation signal into the debugging data. The data storage device receives and saves the debugging data.