An image forming apparatus includes a light emitting element group including a plurality of light emitting elements disposed at first intervals in a first direction, and configured to emit optical beams based on image data, a lens array including a plurality of lenses disposed at second intervals different from the first intervals in the first direction and configured to focus or condense the light emitted from the light emitting element group, and a halftone processing unit configured to perform halftone processing by using a dither matrix corresponding to a relative positional relationship between the plurality of light emitting elements and the plurality of lenses to generate the image data.