1. An image processing apparatus comprising: image input means for photoelectrically converting a document image which has been optically read and for inputting the converted document image as image data; area separation means for separating a plurality of areas included in the input image data from one another; recognition means for performing a character recognition from a plurality of directions with respect to character data in the image data input by said image input means with reference to a character recognition dictionary; first discriminating means for discriminating directional reliabilities of each of the plurality of areas, based on results of the character recognition per direction of a plurality of characters extracted from each area; second discriminating means for discriminating a directional reliability for an entire area of the input image data, based on the discriminated directional reliabilities for each area; and third discriminating means for discriminating a document direction based on the directional reliability for the entire area.