1. An image processing apparatus comprising: an input unit configured to input M-valued image data, where M is an integer equal to or greater than 3; a first processing unit configured to divide the M-valued image data inputted by the input unit into a plurality of pieces of M-valued dividing image data for printing an image on a same area of a print medium through a plurality of printing steps and to convert each of the pieces of the M-valued dividing image data into N-valued dividing image data, where N is an integer equal to or greater than 2, and N is less than M; a second processing unit configured to convert the M-valued image data inputted by the input unit into N-valued image data and to divide the N-valued image data into a plurality of pieces of N-valued dividing image data for printing an image on a same area of a print medium through a plurality of printing steps; and a selecting unit configured to select whether the M-valued image data is to be processed by the first processing unit or by the second processing unit depending on a type of M-valued image data inputted by the input unit.