PURPOSE: To perform recording on both sides of a paper form plural one-side documents in the order of page with high efficiency by a both-side recorder provided with an RDH(recirculating document handler) in a state where the opportunities of the occurrence of the jamming of the document or the paper and the damage and the staining thereof are reduced and the wear and tear of the parts of the both-side recorder is decreased.

CONSTITUTION: As to the first recirculating of the document by the RDH, the document is alternately exposed from the 2nd document so as to form an image on one side of the paper. The paper is stacked on a both-side tray. By deciding whether the last document in the first recirculating is submitted for image forming, whether the number of document is even (in the case of submitting the document for image forming) or odd (in the case of not submitting it for image forming) is decided, and succeeding image forming processes are made different according to the result. In the case of ejecting the paper where the image has been already formed, the paper is ejected by selecting whether the paper is allowed to go by way of a reversal device or not, so that the order of page is arranged.