A plurality of same ink nozzle arrays are provided, and multiple color patches are printed with mutually different dot recording rates respectively using one of the same ink nozzle arrays. Color specification value of the plurality of color patches is measured for each same ink nozzle array. The ink ejection amount error of each same ink nozzle array is determined based on the color specification values of the plurality of color patches for each same ink nozzle array. It is also possible to select among the plurality of color patches a preferable color patch that is closest to a specified reference color patch, and to determine the ink ejection amount error from the dot recording rate of the preferable color patch.