A method of reducing power consumption caused by leakage current in an interface circuit between modules that are driven by different power sources is disclosed. The interface circuit includes an output driver that operates by a first power supply voltage in a first mode and does not operate in a second mode in which the first power supply voltage is prevented from being applied, an input buffer that is operated by a second power supply voltage in the first and second modes, and a transmission line that connects an output terminal of the output driver to an input terminal of the input buffer. The interface circuit further includes a current leakage prevention circuit that prevents, in the second mode, a current leakage in the input buffer between a second power supply voltage source that supplies the second power supply voltage and a ground voltage source.