An image forming apparatus includes: an image forming section to perform an image formation onto a recording medium which moves relatively in a sub scanning direction, the image forming section including a writing unit including a writing element; an image processing section to convert a data for driving the writing unit based on an input image data; a zoom ratio setting section to set zoom ratios of an image in a main scanning direction respectively associated with position in the image in the sub scanning direction; and a controlling section to control the image formation in the writing unit, based on the data for driving the writing unit which has been converted in the image processing section based on the zoom ratio set on the zoom ratio setting section.