A disclosed image forming apparatus includes a reading unit including a light emitting element for emitting light to a record medium, and a light receiving element for receiving reflected light; a print data storing unit storing print data of a uniform pattern which has a color different from a color of the test pattern and is provided in an area including the test pattern, a pattern forming unit printing the test pattern on the uniform pattern after the uniform pattern is printed, a relatively moving unit moving the record medium or the reading unit relatively at a constant speed, a first detection data obtaining unit obtaining first detection data received as the reflection light while the light moves and impinges on the test pattern, and a position detecting unit providing a calculation for determining a position of a line of the test pattern to detect the test pattern.