1. An image processing apparatus comprising: a region segmentation unit configured to perform region segmentation based on a black pixel connected region in a document image; a selection unit configured to select a processing target region from regions segmented by the region segmentation unit; an internal region combining unit configured to generate a combined internal region by combining internal regions which are included in the regions selected by the selection unit and satisfy a predetermined condition; a table region determination unit configured to determine whether a region based on the combined internal region obtained by the internal region combining unit is a table region; and an extraction unit configured to extract the region determined by the table region determination unit as a table region.