An image forming apparatus includes a color registration error amount calculation unit that calculates a color registration error amount from a first test pattern; a correction information obtaining unit that obtains a correction information for correcting an image on a back surface based on previously obtained contraction information of a printing paper after printing an image on a front surface when printing on both surfaces; and an image data correction unit that corrects the image on the back surface based on the color registration error amount calculated by the color registration error amount and the correction information obtained by the correction information obtaining unit.