An image forming apparatus including: a first processing unit configured to subject input image data to tone correction with use of a tone correction table; a second processing unit configured to subject the image data to dither processing; a correction unit configured to correct the image data with use of a correction amount based on positional deviation of scanning lines caused by a mirror face tangle error; a deflection unit configured to deflect light beams emitted from the light source with a mirror face to form the scanning lines; an extraction unit configured to extract a feature amount of the tone correction table; and an adjustment unit configured to adjust a change in tone characteristics in a case where the feature amount extracted by the extraction unit exceeds a predetermined range.