To accurately discriminate a dot region within an image, the image processing apparatus includes first through fourth isolated dot discriminating portions each judging, for each of a plurality of pixels included in the image, whether the pixel corresponds to a center pixel of an isolated dot, an isolated dot size determining portion detecting an isolated dot size, a dot region discriminating portion judging whether a target pixel is included in a dot region based on a position of the pixel judged as being the center pixel of the isolated dot, and a dot region determining portion determining the dot region based on a position of the target pixel judged as being included in the dot region and the detected isolated dot size.