An image forming apparatus which reads a test pattern formed by ejecting liquid droplets onto a recording medium to adjust an ejection timing of the liquid droplets is disclosed. The image forming apparatus includes an image forming unit; a reading unit; a relative movement unit; an intensity data obtaining unit which obtains intensity data on a reflected light which is received from a scanning position of a light by a light receiving unit while the light moves over the test pattern; and a position detection unit which applies a line position determining operation on the intensity data in the vicinity of a point of inflection included between an upper-limit threshold value and a lower-limit threshold value, and detects a position of a line.