The object of the present invention is to use the same FIFO line memory for both enlargement and reduction during variable-magnification processing in the scan direction, allowing reduction in circuit board area, reduction in power consumption, and reduction in cost, and to provide an image processing apparatus that allows variable-magnification processing to be carried out such that the speed of a scanning unit that captures image data during variable-magnification processing in the cross-scan direction is constant. During processing to enlarge an image in the scan direction, image data travels from CCD circuit board, passing through gate b of selector, is written to and read from FIFO memory, and from gate b of selector is written to memory provided at variable magnification unit. At variable magnification unit, image data is read from memory a plurality of times in correspondence to enlargement ratio, changing the magnification of the image data. Furthermore, image data is output through gate a of selector to LSU unit. During processing to reduce an image, image data travels from CCD circuit board, passing through gate a of selector, is input to variable magnification unit where it is subjected to variable-magnification processing, passes through gate a of selector, is written to and read from FIFO memory, passes through gate b of selector, and is output to LSU unit.