An image processing device according to the present application includes an accepting unit and a specifying unit. The accepting unit accepts image data that includes therein at least two diagrams that can be extracted as circles. The specifying unit specifies, by checking a parameter that is calculated from a pair of two circles included in the image data accepted by the accepting unit against a parameter that is calculated from a pair of two perfect circles that have previously been registered as markers that are used for image processing, the pair of the two circles included in the image data as the markers.