The present invention relates to an electronic apparatus having stand-by mode. The electronic apparatus comprises: a first circuit, comprising an interface and transferring data to an external device; a second circuit, comprising a processor and setting a first power supplying mode of the first circuit; and a third circuit, setting a second circuit power supplying mode of the second circuit and setting a second power supply mode of the first circuit when the second circuit is disabled; wherein the processor selects a first circuit power supplying mode from power supplying modes of a plurality of first circuits as the second power supplying mode before the second circuit is disabled.