A data management device such as an image forming device is provided in which usability for handling data stored in boxes is improved. The image forming device includes a hard disk for storing files including image data, an active job database for storing job information about a job of an image output process, a job list generation portion for generating an active job operation screen for letting a user select any one of jobs and producing the screen for the user, a file search portion for searching a file having connection with the job selected by the user on the active job operation screen from the hard disk, and a file list generation portion for producing a file confirmation screen including a list of the searched files for the user.