An illuminating light communication device, which is for establishing a communication system capable of controlling fluctuation in intensity of illuminating light when transmitting data using a power line and illuminating light, and satisfactorily carrying out communication using the power line and communication using the illuminating light, is provided. When data is transmitted through the power line, a signal component is extracted by a filter unit 12, and the demodulated by a power line modulator-demodulator 13, thereby retrieving the data. The retrieved data is temporarily stored in a protocol converter 14. Afterward, the data is converted to the optical communication protocol, and blinking or amount of light of a semiconductor light emitting element 16 is controlled according to the data transmitted from a light source control unit 15, thereby modulating the illuminating light. This allows transmission of data utilizing the illuminating light. Multiple-valued PPM, which defines that existing pulses correspond to OFF while no pulse corresponds to ON, may be used as a modulation system for optical communication.