A misregistration correcting apparatus form an edge list showing information of edges of one scan line from stored drawing objects, updates the formed edge list, and converts the formed edge list into a bit map of one scan line. The updating comprises a first edge list updating that updates the formed edge list on the basis of setting information of a trapping based on characteristics of a printing apparatus and an edge list of a one-line preceding line of the one scan line, and a second edge list updating that updates the edge list on the basis of the trapping setting information and a span showing an outline of the drawing object on the edge list.