A reference voltage training circuit may include: a normal buffer configured to generate a first received signal by receiving one of differential signals based on the other; a calibration signal generation circuit configured to generate a second received signal by receiving the one of the differential signals according to a reference voltage, and generate reference voltage calibration signals by comparing the phase of the second received signal to the phase of the first received signal; and a reference voltage generation circuit configured to calibrate the level of the reference voltage according to the reference voltage calibration signals.