The present invention enables registration adjustments during actual use of an image forming apparatus. A test pattern is formed on a sheet in a full-color image forming apparatus and the test pattern formed on the sheet is read in an image read unit. From the result of reading the test pattern, misregistrations of vertical and horizontal scaling factors, parallelism, squareness, skew, side registration, and lead registration in the test pattern are determined, and mounting positions, drive timings, drive speeds, and the like of constituent members are adjusted.