1. An image processing apparatus, comprising: an area division unit configured to divide an image of a page into a plurality of areas; an attribute information addition unit configured to add, to the plurality of divided areas, attribute information depending on an attribute determination of each of the areas so that when one of the areas is determined to be a caption area, caption attribute information is added to the caption area, when another of the areas is determined to be a body text area, body text attribute information is added to the body text area, and when another of the areas is determined to be an object area, object attribute information is added to the object area; a character recognition unit configured to perform a character recognition processing on a caption area and a body text area; and a metadata processing unit configured to associate metadata with an object area accompanied by a caption area, wherein the metadata processing unit comprises: a first extraction unit configured to extract, from the result of the character recognition processing on the caption area, an anchor expression composed of a predetermined character string and a caption expression composed of a character string other than the anchor expression; a first determination unit configured to determine whether there are a plurality of object areas accompanied by caption areas including an identical anchor expression; a second extraction unit configured to extract, from the result of the character recognition processing on the body text area, an explanatory text including the anchor expression; a first association unit configured to associate, in the case that the first determination unit determines that there is one object area accompanied by a caption area including the identical anchor expression, the determined one object area with metadata obtained from the explanatory text extracted by the second extraction unit; a similarity degree calculation unit configured to calculate, in the case that the first determination unit determines that there are a plurality of object areas accompanied by caption areas including the identical anchor expression, similarity degrees between caption expressions of the respective caption areas including the identical anchor expression and the explanatory text including the anchor expression extracted by the second extraction unit, respectively; and a second association unit configured to determine, based on the similarity degrees calculated by the similarity degree calculation unit, the explanatory texts that are optimal for the respective plurality of object areas accompanied by caption areas including the identical anchor expression and to associate metadata obtained from the determined optimal explanatory texts to the respective plurality of object areas accompanied by caption areas including the identical anchor expression.