An image processing device is disclosed that classifies images in an image database and displays the classified images for searching, and is able to easily narrow a range of candidate images and improve operability. The image processing device includes a first classification unit, a display image controller that generates a display image for displaying a status of the classification performed by the first classification unit; a second classification unit that enables a user to select one or more categories included in the display image, and classifies image documents included in a selected category; a detection unit that detects a searching status; and a classification key selection unit that selects a classification key for the second classification unit in response to detection results of the detection unit.