A background discriminating unit for discriminating the state of background of an input image. An adaptive quantizer quantizes the input image based upon the state of the background to form a bi-level image of the background. An area partitioning unit partitions the input image into areas based upon the bi-level image of the background. Each area resulting from partitioning is coded by a multivalued image coder or bi-level image coder in dependence upon the characteristic of the area. Accordingly, an input image can be partitioned into areas correctly based upon the characteristics of the area and the areas obtained by partitioning can be coded in conformity with the characteristic of the area.