To minimize the occurrence of a jam, when the size of printing-set paper is different from actual paper, while improving throughput by starting paper feeding-carrying of second paper, before finishing detection of the length of first paper.

When the rear end is not detected by a registration sensor (Step S303), whether or not to start paper feeding of succeeding paper is checked (Step S304). When the paper feeding is started, a predetermined value 1 is applied (Step S305). When the paper feeding is not started, a predetermined value 2 is applied (Step S306). When the rear end is not detected even if a timer passes by " prediction time + the predetermined value " (Step S307), a determination is made that there is risk of causing the jam (Step S308). When the rear end is detected before the timer passes by " the prediction time + the predetermined value " (Step S303), operation is finished without determining as the jam. The jam by a setting error can be reduced by being set in the predetermined value 1 less than the predetermined value 2.