To make an image forming apparatus carrying a multi-core CPU, generate printing data at a higher speed, even when it is made to generate an intermediate code of the printing data that assigns a plurality of pages to one page.

In the image forming apparatus, when a time estimated by an estimating means is longer than a time for the image forming apparatus to print one sheet, a first processor converts the printing data of predetermined logic pages to be printed on a first printing paper to the intermediate code, and a second processor converts the printing data of logic pages other than the predetermined logic pages to be printed on the first printing paper to the intermediate code (S311).