An apparatus outputs a first number of printed materials, reads the first number of printed materials output to acquire the first number of pieces of scanned image data, the first number being two or more, and controls a density of output printed materials by calculating variations in lightness values in the respective pieces of scanned image data included in scanned image data groups for each scanned image data group having as a unit a second number of pieces of scanned image data consecutive in order of being read among the first number of pieces of scanned image data, the second number being two or more, so that the printed materials are further output until all the variations in the lightness values are less than a first threshold value.