An apparatus comprising: a main system that controls the apparatus; a plurality of sub-systems (11, 12, 13) that are connected to the main system in a communicatable manner and that implement various functions; and a power supply control unit that applies power to the main system and plurality of sub-systems (11, 12, 13); the main system including a power mode designating unit that outputs a command that indicates ON/OFF of output of supply voltage to the power supply control unit; one of the sub-systems being an operating unit control system including a sub-central processing unit that controls the operating unit control system; characterized in that: the power mode designating unit further outputs an operation mode designating signal that designates either one of a normal operation mode and a power-saving mode to the sub-power supply control unit of the operating unit control system; and the operating unit control system further includes a sub-power supply control unit that supplies to the sub-central processing unit, in the normal operation mode, a first voltage with which driving of the sub-central processing unit is possible, while in the power-saving mode, supplies to the sub-central processing unit a second voltage that is lower than the first voltage, with which driving of the sub-central processing unit is impossible but retention of condition is possible; and in that when shifting to the power-saving mode is possible, the sub-central processing unit outputs a power-saving mode shift enable signal indicating that shifting to the power-saving mode is possible to the sub-power supply control unit, and when the operation mode designating signal designates the power-saving mode and the power-saving mode shift enable signal indicates that shifting to the power-saving mode is possible, the sub-power supply control unit supplies the second voltage to the sub-central processing unit. a main system that controls the apparatus; a plurality of sub-systems (11, 12, 13) that are connected to the main system in a communicatable manner and that implement various functions; and a power supply control unit that applies power to the main system and plurality of sub-systems (11, 12, 13); the main system including a power mode designating unit that outputs a command that indicates ON/OFF of output of supply voltage to the power supply control unit; one of the sub-systems being an operating unit control system including a sub-central processing unit that controls the operating unit control system; characterized in that: the power mode designating unit further outputs an operation mode designating signal that designates either one of a normal operation mode and a power-saving mode to the sub-power supply control unit of the operating unit control system; and the operating unit control system further includes a sub-power supply control unit that supplies to the sub-central processing unit, in the normal operation mode, a first voltage with which driving of the sub-central processing unit is possible, while in the power-saving mode, supplies to the sub-central processing unit a second voltage that is lower than the first voltage, with which driving of the sub-central processing unit is impossible but retention of condition is possible; and in that the power mode designating unit further outputs an operation mode designating signal that designates either one of a normal operation mode and a power-saving mode to the sub-power supply control unit of the operating unit control system; and the operating unit control system further includes a sub-power supply control unit that supplies to the sub-central processing unit, in the normal operation mode, a first voltage with which driving of the sub-central processing unit is possible, while in the power-saving mode, supplies to the sub-central processing unit a second voltage that is lower than the first voltage, with which driving of the sub-central processing unit is impossible but retention of condition is possible; and in that when shifting to the power-saving mode is possible, the sub-central processing unit outputs a power-saving mode shift enable signal indicating that shifting to the power-saving mode is possible to the sub-power supply control unit, and when the operation mode designating signal designates the power-saving mode and the power-saving mode shift enable signal indicates that shifting to the power-saving mode is possible, the sub-power supply control unit supplies the second voltage to the sub-central processing unit.