In the image forming apparatus, a color shift correction execution check unit detects positions of density correction patches of respective colors according to binary signals of density detection outputs by a density sensor on the density correction patches. When distances corresponding to intervals of time from starts of image drawing of the density correction patches of the respective colors to the detection of the positions of the density correction patches of the respective colors and distances between the density correction patches of the respective colors are shifted from a value, the color shift correction execution check unit determines color shift correction processing is required to be executed, and it gives an instruction to a color shift correction control unit to execute the color shift correction processing. And the color shift correction control unit forms a color shift correction patch to execute the color shift correction processing.