A technique that can stably realize highly accurate image adjustment processing even when unexpected toner density unevenness occurs on an identical sheet because of fluctuation in an image formation characteristic and the like is provided.
An image forming apparatus that forms, on a sheet, a test pattern formed by a color obtained by mixing colors of toners of plural colors, reads a test pattern image formed on the sheet with a color sensor, and performs predetermined image adjustment processing on the basis of information read includes a halftone-image forming unit configured to form, on the sheet, at least one of a first halftone image extending over a predetermined range in a main scanning direction and a second halftone image extending over a predetermined range in a sub-scanning direction, an image reading unit configured to read the halftone image formed on the sheet by the halftone-image forming unit, a density-unevenness determining unit configured to determine, on the basis of information read by the image reading unit, toner density unevenness in an image formed by the image forming apparatus, an image-adjustment processing unit configured to perform the predetermined image adjustment processing on the basis of the density unevenness determined, and a color sensor that is arranged on a downstream side of a fixing device in a sheet conveyance direction and reads the test pattern formed on the sheet.