A printing apparatus executes a series of print commands from a host computer and controls a printer engine equipped with a rotation-type double-side printing mechanism. The printing apparatus comprises page buffers, a drawing-processing unit for drawing data on the page buffers. and a printing-processing unit for processing printing of a drawn data. The printing-processing unit determines whether the drawn data to be printed is first or second-half page is to be performed, and immediately starts printing of first-half if first-half page is determined or puts printing of the second-half page in a wait state if second-half page is determined. The printing-processing unit releases the printing of the second-half page from the wait state when a predetermined condition has been detected. The predetermined condition can be that the number of sheets retained in the printing mechanism has reached a predetermined maximum number or that a final page of a document has been detected by receiving a command indicating the end of a double side printing. The predetermined condition can also be that a change of sheet-sizes, a change of paper supply units or a change of paper-eject units has been detected.