To obtain a reduced image with high image quality, excellent graininess and gradation reproduction characteristics by dividing inputted image information into plural pixel columns, specifying the pixel column with optimal characteristics value in image reproduction among the plural pixel columns and generating a first pixel column by synthesizing only the specified optimal pixel columns.

Image memory part 151 is provided with a pixel column storage part 151A to store information to specify an output buffer to output the pixel column with the best SN ratio. The pixel column is synthesized only from output of the output buffer to output the pixel column with excellent SN ratio, based on the information to specify the output buffer stored in the pixel column storage part 151A. The pixel column is outputted to a variable magnification processing part 16 with a shading correcting part 14 by an output synthesizing part 13. The pixel column is generated by performing a thinning processing to the pixel column received from the output synthesizing part 13 through a shading correcting part 14 by the variable magnification processing part 16.