A color printer 20 allocates all of the image processing memory resources for image processing on image data GD lined up in the main scanning direction of a print head IH, secures an amount of memory resources for each of the lined up image data GD, and releases the memory resources as the image processing completes. A CPU 51 secures image processing memory resources for an image datum 1 in the storage area of a RAM 53, and releases the secured memory resources when the image processing on the image datum 1 is complete. The CPU 51 repeatedly implements this processing on each image datum contained in one print job.