An image processing device that executes a job based on instruction operation by a user authenticated as a result of user authentication, comprises a human body communication controller that makes human body communication with a human body communication terminal held by a user through at least one human body communication antenna arranged around a device body, and an authenticating unit that performs user authentication based on user information the human body communication controller acquires from said human body communication terminal. The human body communication controller makes the human body communication terminal shift from a communication mode to a power-saving mode in response to authenticating a user by the authenticating unit.