An image processing apparatus for storing an image of an original and outputting an entire area or partial area, referred to as output area, of the stored image of the original as a color image or a monochrome image, the apparatus comprising: an area setting unit for setting a plurality of areas, the output area being one of the set areas; a color determination unit for determining whether the original is in color or monochrome in each of the areas set by the area setting unit on the basis of the image of the original; and a unit (108,109) for storing a result of determination made by the color determination unit on the image of the original as accessory information on the image of the original, wherein the color determination unit includes a block color determination processing unit for dividing the image of the original into a plurality of first blocks and determining whether or not each of the first blocks is a color image area, and an area color determination processing unit for determining whether the original is in color or monochrome in each of the areas set by the area setting unit on the basis of a result of determination made by the block color determination processing unit on the first blocks included in the respective area set by the area setting unit, characterized in that the block color determination processing unit determines whether each of the first blocks into which the image of the original is divided is a color image area, a monochrome image area, or an ambiguous image area; divides the image of the original into a plurality of second blocks that lie in shifted positions relative to the first blocks, and determines whether each of the second blocks is a color image area or a monochrome image area; and corrects the result of determination on a first block that is determined to be an ambiguous image area to either a color image area or a monochrome image area on the basis of the result of determination on second blocks that overlap the first block. an area setting unit for setting a plurality of areas, the output area being one of the set areas; a color determination unit for determining whether the original is in color or monochrome in each of the areas set by the area setting unit on the basis of the image of the original; and a unit (108,109) for storing a result of determination made by the color determination unit on the image of the original as accessory information on the image of the original, wherein the color determination unit includes a block color determination processing unit for dividing the image of the original into a plurality of first blocks and determining whether or not each of the first blocks is a color image area, and an area color determination processing unit for determining whether the original is in color or monochrome in each of the areas set by the area setting unit on the basis of a result of determination made by the block color determination processing unit on the first blocks included in the respective area set by the area setting unit, characterized in that the block color determination processing unit determines whether each of the first blocks into which the image of the original is divided is a color image area, a monochrome image area, or an ambiguous image area; divides the image of the original into a plurality of second blocks that lie in shifted positions relative to the first blocks, and determines whether each of the second blocks is a color image area or a monochrome image area; and corrects the result of determination on a first block that is determined to be an ambiguous image area to either a color image area or a monochrome image area on the basis of the result of determination on second blocks that overlap the first block.