In an image forming device including a processor unit, a first screen generating part generates a screen to be displayed on an operation panel and displays the screen on the operation panel. A second screen generating part generates screen data to be displayed on an information processing device and transmits the screen data to the information processing device. An application managing part selects, in response to a request of execution of an application, one of the first and second screen generating parts as a candidate for use of the application based on a source inputting the request. The first and second screen generating parts are configured to receive a request of generation of a screen using a common interface, and the application inputs through the common interface the request to the selected one of the first and second screen generating parts.