An image forming apparatus according to the invention is characterized by including; an input unit that inputs first color data; a first color converting unit that converts the first color data into a black single color data; a second color converting unit that converts the first color data into second color data; a brightness correcting unit that corrects brightness of the black single color data such that brightness of the black single color data converted by the first color converting unit is equal to brightness of the second color data converted by the second color converting unit; and an image forming unit that prints image data on a recording medium. According to the image forming apparatus, in the image forming apparatus that uses both color conversion processing and black conversion processing, even if image data continuously changes from a chromatic color to an achromatic color, it is possible to reduce “brightness discontinuity”.