PURPOSE: To ensure the reprinting of only an unprinted page, by a method wherein, a back-up memory saving the bit data written in a drum is provided, and in the occurrence of paper jamming the bit data corresponding to the unprinted page is read and written in the drum.

CONSTITUTION: The bit data read from a bit map memory 4 is written in a drum 6 to be printed on a paper, and the printed paper is stacked in a stacker 7. At this time, the same data as the bit data written in the drum is successively saved in a back up memory 5 correspondingly to the pages. In the occurrence of paper jamming, on the basis of a printed page number informed from the stacker 7, a page detection circuit 8 searches the bit data for the unprinted page from the back-up memory 5, and a transfer control circuit 9 transfers the bit data of the unprinted page to the bit map memory 4 to make it reprinted. Therefore, the paper jamming is recovered after a paper with a page number which has not been stacked in the stacker 7 as a printed page number is surely reprinted.