A luminance nonuniformity adjustment module for eliminating luminance nonuniformities in light emitting elements determines a luminance correction coefficient for each light-emitting element through a test print. The luminance nonuniformity adjustment module comprises a provisional luminance correction coefficient calculation unit, an improper coloring degree calculation unit and a luminance correction coefficient determination unit. The provisional luminance correction coefficient calculation unit calculates a provisional luminance correction coefficient by comparing a measured density value for a grayscale chart and a predetermined target density value. The improper coloring degree calculation unit calculates an improper coloring degree, which is the degree of improper coloring that occurs when other colors are expressed when developing a specific color, from the measured density values for the grayscale chart and an unbalanced chart in which the gray balance has been altered. The luminance correction coefficient determination unit corrects the provisional luminance correction coefficient using the improper coloring degree.