1. An area testing method for deciding a type of an area included in a target image to be a target of image processing, the method comprising: generating an edge image in accordance with the target image; generating a first histogram indicating the number of edge pixels that exist in the lateral direction at each position in the longitudinal direction within a predetermined area and a second histogram indicating the number of the edge pixels that exist in the longitudinal direction at each position in the lateral direction within the predetermined area, the edge pixels indicating an edge in the predetermined area of the generated edge image; determining a variance value of a width of a mountain having an extreme value that exceeds a predetermined threshold value in the generated first histogram and second histogram; and deciding whether or not the predetermined area is at least one of a table area and a graph area based on the determined variance value.