An image forming apparatus of the present invention includes (i) an image interpolating section for calculating interpolation point and interpolation density of the interpolation point when subjecting a binary image to resolution conversion and scaling and (ii) an offset amount correcting section for giving an offset beforehand when the image interpolating section calculates the interpolation point. As a result, the image forming apparatus can comply with unrounded magnifications of other than integral multiples and a desirable image even with respect to a character image and a pseudo-halftone image.