According to one embodiment, a bus buffer circuit includes an input buffer circuit that receives an input signal, and outputs a non-inversion input signal and an inversion input signal, a voltage conversion circuit that operates by a second power supply, performs voltage conversion on the non-inversion input signal and the inversion input signal input thereto, and outputs the signals as a voltage-converted non-inversion output signal and a voltage-converted inversion output signal, an output retaining circuit that retains the voltage-converted non-inversion output signal and the voltage-converted inversion output signal at a same potential level when an output enable signal is in a disable state, a determinator that determines whether these signals are at a same potential level, a three-state output buffer circuit that outputs the voltage-converted non-inversion output signal or the voltage-converted inversion output signal from an output terminal, and an output controller that sets the three-state output buffer circuit in an output disable state, when the voltage-converted non-inversion output signal and the voltage-converted inversion output signal are at a same potential level, on a basis of an outcome of the determinator. Therefore, it is possible to prevent a potential different from the actual bus signal from being temporarily output during an output state transition, in a case where the state is fixed to reduce the power consumption.