To appropriately extract a character region from an image including a boundary between a shadow and a sunny place.

Smoothing processing and edge extraction processing are operated to an object image, and first labeling processing for classifying the image for every continuous region is operated to the processed image, and the region whose size is larger than an upper limit size as a predetermined character is erased in the respective continuous regions whose labeling has been operated by the first labeling processing, and expansion/contraction processing is operated to the erased image, and second labeling processing is operated to the contracted image, and the region included inside the region whose labeling has been operated by the second labeling processing is detected in the respective regions whose labeling has been operated remaining in the erased image (image before expansion/contraction), and the detected region is erased from the erased image.