An image forming device and a print file storage method thereof, in which a file name of a print file transmitted from a host apparatus can be automatically modified to a file name designated by a user at a time of storing the file. The image forming device includes a storage part including a folder to store print files transmitted from external apparatuses, a user interface to set a storage environment of the folder so that the file name of the print file can be modified, a controller to control the file name to be modified and stored in the folder according to the set storage environment, when the print file is stored in the folder. When the file name of the print file transmitted from the external apparatuses is stored in a predetermined order according to the file name or a folder name designated by the user, it is possible to automatically modify and store the file name of the print file without input by the user.