An image forming apparatus includes a photoconductor drum, a first printer head that forms a first pattern on the photoconductor drum and has a first end part, a second printer head that forms second and third patterns on the photoconductor drum and has a second end part that overlaps the first end part in a main scanning direction, a detection sensor that detects the densities of first and second test patterns formed at an area of the photoconductor drum at which the first and second end parts overlap, the first test pattern being formed by combining the first and second patterns, the second test pattern being formed by combining the first and third patterns, and a determination part that determines a deviation direction between the first and second printer heads by comparing the densities detected by the detection sensor.