Disclosed is an image processing apparatus in which vector data from which noise has been removed and amount of data reduced can be generated in ideal fashion with regard to an illustration area selected from a document image. The document image is input to the apparatus and is segmented into a plurality of areas. A clip-art image is selected from these areas and a plurality of clusters are generated with regard to this image area. When a small area included in the plurality of clusters is determined as a noise, the noise is eliminated by combining the small area with a adjacent cluster. After noise is removed, the cluster group eventually obtained is converted to vector data.