An image forming apparatus which reads a test pattern formed onto a recording medium to adjust an ejection timing of liquid droplets is disclosed. The apparatus includes a reading unit; a pattern data storage unit; an image forming unit; a relative movement unit; an intensity data obtaining unit which obtains intensity data on a reflected light which is received by a light receiving unit from a scanning position of a light while the light moves over the test pattern; and a position detecting unit which applies a line position determining operation on the intensity data and detects a line position.