An image forming apparatus includes an image forming section for forming a toner image using light color toner and dark color toner, which have the same hues and which have different densities. A detecting section detects a density of a toner image which is formed for reference by the image forming section. The reference toner image includes a number of portions corresponding to different image density levels. A control section controls an image forming condition of the image forming section in accordance with an output of the detecting section. A difference between the image density levels corresponding to adjacent portions in a density area where an image is formed using both of the light toner and the dark toner is smaller than that in an image density area where an image is formed using only the light toner.