1. An image information processing apparatus comprising: inputting means for sequentially inputting a plurality of documents as image information; detecting means for detecting a separating sheet with a white specified area, the separating sheet being inserted between the documents; separation designating means for designating a grouping of the image information according to a position of the separating sheet inserted; and memory means for separating the image information into groups in accordance with an output of said separation designating means and filing each of said group of the image information as a block of document data, wherein said detecting means carries out a logical AND between image data of said specified area of the separating sheet and data which is obtained by shifting the image data by an amount of one dot in a lateral direction, and detecting the separating sheet based on first data represented by the logical AND so as to eliminate noise from the image information.