PURPOSE: To attain quick processing without loss of an image of picture informa tion even when the reduction rate is increasing by using OR of picture element signals along a diagonal line of plural picture element areas resulting from dividing the picture information as a representative value.

CONSTITUTION: Picture information is divided into plural areas each comprising n-picture elements × n-picture elements, and OR of picture element signals along a diagonal line of the said area is calculated as a representative value. For example, when read picture information is reduced to 1/4, the information is divided into areas 1-4 each comprising 4-picture elements × 4-picture elements, four picture element signals on a diagonal line from the upper left to the down right direction are ORed as to each of the areas 1-4, then representative values 1-4 of the areas 1-4 are decided and read picture information is reduced with a reduction rate of 1/n. Graphic information comprising lateral and longitudinal lines in the picture information is maintained to reduce black level deformation of the reduced picture through the reduction method above, and even when the reduction rate is increased, the image of the picture information is not lost and quick processing is implemented.