To reduce a processing time while reducing a storing region for use when performing a printing two or more images in two or more number of copies.

A printer 20 develops the image data to be printed into coloring agent classification page data which is the page data decomposed into the sheet for each color stored in an ink cartridge 26 when printing two or more images in two or more number of copies, and stocks the coloring agent classification page data whose development time is longer than any one, in RAM 44 having two or more storing regions. At this time, the coloring agent classification page data of the longer development time is preserved in a preservation area 44b while securing an area for development 44a by opening the preservation area 44b wherein the data of the shortest development time is stored and using it as the area for development 44a. Thus, the coloring agent classification page data of long development time is stocked in RAM 44 more preferentially, and then the stocked page data is used for next printing.