An image forming apparatus forms an image by irradiating light from a light source to an image carrier. The image forming apparatus includes: an image processing unit that processes image data at resolution N; and a control unit that generates modulation data to drive the light source at resolution m×N (m is a positive integer equal to or larger than 2), which is higher than the resolution N, based on the processed image data. Processing at the image processing unit is pseudo-halftone processing to perform line thinning or thickening on a part of the image data. The control unit converts the image data at the resolution N that has been subjected to the pseudo-halftone processing into data at the resolution m×N, and adjusts an amount of light for a part of the image data based on the resolution m×N.