By executing low-speed conveyance of web by a web feeding mechanism before the printing operation begins, slack W22a, W10a, and W15a in the web located downstream of the guide rollers, and the slacked web is accumulated in the air loop portion, thereby completing the standby for printing. At that time, the amount of web conveyance (accumulation) is saved. Then, high-speed printing operation begins, and when the amount of printing has reached the amount of web conveyance saved, high-speed conveyance by the web feeding mechanism begins.