An image forming apparatus includes an image forming device which forms an image on a rotation member, a sensor, and a controller. The controller executes an overlapping pattern detection processing which detects a positional deviation amount using an overlapping pattern including a plurality of overlapping marks with overlapped colorant images of two colors, a non-overlapping pattern detection processing which detects a positional deviation amount using a non-overlapping pattern including a plurality of marks, each having a single color, and an execution processing which executes the overlapping pattern detection processing or the non-overlapping pattern detection processing based on a condition.