A data relay apparatus according to one embodiment described herein can include a phase detection unit that can detect a phase difference between a clock output from a transmitter and a clock output from a receiver, and generate a plurality of phase detection signals, a data relay control unit that can distinguish a difference in clock timing between the clocks of the transmitter and the receiver in response to the plurality of phase detection signals, and output a relay data selection signal and a relay control clock, and a data relay unit that can transmit data output from the receiver to the transmitter in response to the relay data selection signal and the relay control clock.