An ink-jet printer in which drive data for a print head is converted into a light signal by a first light-emitting diode provided in a control circuit. The light signal is transmitted, through an optical fiber, to a first photo-diode provided in a receiver circuit. The light signal received by the first photo-diode is converted into an electric signal. Data concerning the status of a print head unit is converted into a light signal by a second light-emitting diode provided in the receiver circuit. The light signal is transmitted from the second light-emitting diode, through the optical fiber, to a second photo-diode provided in the control circuit. The light signal received by the second photo-diode is converted into an electric signal.