A transmission apparatus of a wireless light communication system using an illumination light source can maximize a rate of data transmission while maintaining a brightness adjusting function of the illumination light source. The transmission apparatus includes a dimming level input unit which receives a dimming level of the illumination light source as an input, a coder which codes original data and outputs the coded data, a dimming coder which checks the dimming level input to the dimming level input unit, generates a symbol-codeword table corresponding to the dimming level, and dimming-codes the data output from the coder, a line coder which converts the data diming-coded by the dimming coder into pulse signals.