An image processing apparatus includes an interface through which scanned image data obtained by scanning a designated region, is acquired, and a processor. The processor extracts a contour line representing a document area from the scanned image data, extracts vertices of the contour line, determines whether a plurality of original documents is present in the document area based on the vertices, extracts document image data of each original document from the scanned image data, and generates one file including the extracted document image data for each original document.