An image forming apparatus for forming images by outputting plural image data in an order corresponding to an input order of plural input data is disclosed. The image forming apparatus includes a data receiving part for receiving the input data, a priority determining part for determining priority of outputting the input data, a PDL process part having plural PDL interpretation parts including at least first and second PDL interpretation parts for performing a PDL process on the input data, and a PDL control part for controlling each of the plural PDL interpretation parts, wherein when a subsequent input data is determined to have a priority higher than that of a prior input data in a case where the first PDL interpretation part is performing a first PDL process on the prior input data, the PDL control part is configured to stop the first PDL process and cause the second PDL interpretation part to perform a second PDL process on the subsequent input data.