An image formation assisting device calculates layout information such as allocation and pasting position of each page by a BEP from a file size with reference to the orientation tag of image file data in a TIFF produced by an RIP and cuts image data electronically according to the result of the calculation and makes the upper portion and lower portion of each page correspond with those of the other papers and rearranges each electronically cut page according to an instruction of collation or face-down, when the instruction is provided, and activates a print engine to start and specifies predetermined paper automatically and outputs the image data to the print engine. As a result, there is provided an image formation assisting device capable of using image data for CTP for on-demand printing.