The printer includes a CPU, a bridge image processing unit, a RAM, a ROM, a supply power control unit, a printing unit, a communication I/F, and physical layer I/Fs. When the Ethernet is connected to the communication I/F, if the DMA transfer request signal is not outputted from the DMAC for more than a specific time, the supply power control unit shifts into the sleep mode that halts the supplies of clock to the CPU, etc.; and if data is received from the host computer group, the supply power control unit releases the sleep mode. Further, in case that equipment conforming to the USB standard or the IEEE 1284 is connected to the communication I/F, if the DMA transfer request signal is not outputted from the DMAC for more than the specific time, the supply power control unit shifts into the power halt mode that halts the supply of power to the CPU, etc. Thus, the invention provides a printer capable of effectively reducing the power consumption.