An electronic apparatus characterized in that includes: a wireless tag that stores information; a memory; a power-supply-control unit that controls a power-supply mode including a normal mode and a plurality of modes other than the normal mode; a system-control unit that instructs the power-supply-control unit to switch the power-supply mode from a current power-supply mode to the normal mode based on the information when the current power-supply mode is a power-saving mode or a power-supply-OFF mode; the normal mode is a mode in which power is supplied to each of parts of the electronic apparatus and functions of the electronic apparatus can be used; and the plurality of modes includes the power-saving mode and the power-supply-OFF mode, the power-saving mode includes a low-power mode in which reduces the power consumption and a sleep mode in which the power consumption is less than in the low-power mode, the power-supply-OFF mode is a mode that stops supplying power to parts other than at least the system-control unit; wherein the system-control unit acquires, in response to a read request that is transmitted from a user-authenticated portable terminal, the current power-supply mode of the power-supply-control unit, stores power-supply-mode information that corresponds to the acquired power-supply mode in the memory, and writes the power-supply-mode information that corresponds to the acquired current power-supply mode to the wireless tag to cause the portable terminal to read the power-supply-mode information written in the wireless tag, and when there is writing of power-supply-mode-switch-request information that corresponds to the power-supply-mode information written in the wireless tag and that is included in a write request from the user-authenticated portable terminal to the wireless tag, the system-control unit instructs the power-supply-control unit to switch to a normal mode based on the power-supply-mode-switch-request information and from the power-supply-mode information written in the wireless tag, and when the portable terminal is separated from the wireless tag, acquires the power-supply-mode information stored in the memory and instructs the power-supply-control unit to return to the power-supply mode before the instruction. a wireless tag that stores information; a memory; a power-supply-control unit that controls a power-supply mode including a normal mode and a plurality of modes other than the normal mode; a system-control unit that instructs the power-supply-control unit to switch the power-supply mode from a current power-supply mode to the normal mode based on the information when the current power-supply mode is a power-saving mode or a power-supply-OFF mode; the normal mode is a mode in which power is supplied to each of parts of the electronic apparatus and functions of the electronic apparatus can be used; and the plurality of modes includes the power-saving mode and the power-supply-OFF mode, the power-saving mode includes a low-power mode in which reduces the power consumption and a sleep mode in which the power consumption is less than in the low-power mode, the power-supply-OFF mode is a mode that stops supplying power to parts other than at least the system-control unit; wherein the system-control unit acquires, in response to a read request that is transmitted from a user-authenticated portable terminal, the current power-supply mode of the power-supply-control unit, stores power-supply-mode information that corresponds to the acquired power-supply mode in the memory, and writes the power-supply-mode information that corresponds to the acquired current power-supply mode to the wireless tag to cause the portable terminal to read the power-supply-mode information written in the wireless tag, and when there is writing of power-supply-mode-switch-request information that corresponds to the power-supply-mode information written in the wireless tag and that is included in a write request from the user-authenticated portable terminal to the wireless tag, the system-control unit instructs the power-supply-control unit to switch to a normal mode based on the power-supply-mode-switch-request information and from the power-supply-mode information written in the wireless tag, and when the portable terminal is separated from the wireless tag, acquires the power-supply-mode information stored in the memory and instructs the power-supply-control unit to return to the power-supply mode before the instruction.