1. An image processing device comprising area deciding means for discriminating an objective pixel to be of a character image area or a halftone image area by sequentially checking pixels of multi-gradational image data, pixel by pixel, character-binarizing means for binarizing character image areas, photograph-binarizing means for binarizing halftone image areas, and output means for selectably outputting binarized data for character and binarized data for halftone according to the area decision results; wherein the area deciding means for discriminating the objective pixel to be of a character image area or a halftone image area by sequentially checking pixels of multi-gradational image data pixel by pixel decides which area a particular pixel is in by reference to a set of pixels consisting of four pixels at the following locations: (a) above and to the left of a pixel located above and to the left of the particular pixel, (b) above and to the right of a pixel located above and to the right of the particular pixel, (c) below and to the left of a pixel located above and to the left of the particular pixel, and (d) below and to the right of a pixel located above and to the right of the particular pixel.