1. An image processing device comprising: a feature data storage unit which stores feature data indicating a feature of appearance of an object; a superimposition display data storage unit which stores superimposition display data which is to be a source of an image that is superimposed on a visual field of a user and an item position which is a position of an item forming the superimposition display data; an environment map generating unit which generates an environment map representing a position of one or more objects existing in a real space based on an input image obtained by imaging the real space using an imaging device and the feature data stored in the feature data storage unit; a superimposition display position determining unit which determines a position of an object having a predetermined flat surface or curved surface out of an object imaged in the input image based on the environment map; a superimposition display image generating unit which generates a superimposition display image by setting the superimposition display data at the position of the object determined by the superimposition display position determining unit; an image superimposing unit which superimposes the superimposition display image on the visual field of the user; an operating object recognizing unit which recognizes an operating object imaged in the input image; and a process executing unit which executes a process corresponding to the item selected based on a position of the operating object recognized by the operating object recognizing unit.