1. An image processing device that performs image processing for first and second functions, comprising: a time management unit that is configured to manage time; a memory unit that is configured to store image processing restriction information that defines time of day restrictions for the first function and time of day restrictions for the second function; a device management unit that is configured to receive an image processing request for image processing of one of the first and second functions; and an image processing restriction unit that is configured, based on the time managed by the time management unit, a time of the image processing request and the image processing restriction information, to determine an image processing restriction corresponding to the first function if the device management unit receives the image processing request for image processing of the first function, and determine an image processing restriction corresponding to the second function if the device management unit receives the image processing request for image processing of the second function, wherein the device management unit is configured to perform one of the image processing restriction corresponding to the first function and the image processing restriction to the second function, based on a determination made by the image processing restriction unit.