To obtain a binary picture reducing processor for speedily realizing the processing of reducing a binary picture by making multilevel by minimum number of arithmetic times whatever filter is used.

A 2N:1 multi-valuing and reducing part 14 filters the binary picture expressed by one pixel and one bit through the use of a filter for 2:1 reduction to generate multilevel to accelerate processing until reducing an inputted picture to 2:1. In addition, the processing is repeated by the number of times (N-1 times) decided by a thinning rate dividing control part 12 to generate an M-level picture of 2N:1 reduction to generate an M-level reduced picture by small number of product sum arithmetic times. In addition, an additional reducing processing part 17 reduce-processes the picture generated by the part 14 by the magnification decided by the part 12 to generate the M-level reduced picture of an inputted and desired magnification.