1. A method of executing area-division and compression of a document image, comprising: sectionalizing said document image on the basis of attributes associated with a compression mode to form a plurality of image areas each having an attribute associated with the compression mode; determining whether said image areas partly or fully overlap with one another to form an overlap area; separating said overlap area from said overlapping image areas if said overlap area has been formed, and newly setting an attribute associated with the compression mode for said overlap area according to priorities of the respective attributes of said overlapping image areas, and the positional relationship between said overlap area and each of said overlapping areas; and compressing each of said image areas and said overlap area using a compression technique corresponding to the attribute of said respective area.