Image forming apparatus and auto color registration method of the same

An image forming apparatus which forms a color image on a print medium by overlapping an image formed in each color, the image forming apparatus comprising:

• a plurality of developing units which each developing unit develops a color image in a predetermined color;
• a transfer unit which transfers the color image developed by the plurality of developing units to the print medium and comprises a transfer belt rotatably installed on a transfer path;
• a first detector which is provided in a predetermined location of the transfer belt to face the transfer belt and detects any defect from a surface of the transfer belt;
• a second detector which is provided in a predetermined location of the transfer belt to face the transfer belt and detects a test pattern of an auto color registration (ACR) error transferred to the transfer belt;
• and
• a controller,
• wherein, if there is a defect from the surface of the transfer belt, the controller is configured to adjust data on the test pattern of the ACR error formed in a defective location of the transfer belt detected by the first detector by using the defective location information, and
• if there is no defect from the surface of the transfer belt, the controller is configured to cause the data on the test pattern of the ACR error to not be adjusted according to a detection result of the first detector which detects no defect from the surface of the transfer belt.