Abstract: An image forming apparatus includes a print data memory 34 for storing print data inputted, a printing unit for printing (13, 24) on a sheet of recording paper 23 based on the printing data stored in a print data memory 34, a first waiting unit (12) for making a sheet of recording paper 23 already printed on one side by the printing means wait, a controller 18 which reads printing data for two pages succeeding the page printed on the preceding recording paper 23 into the print data memory 34 and expands the data into a printable state after the recording paper 23 has left for the first waiting unit (12), and then, feeds the succeeding recording paper 23 to the printing unit (13, 24) to print on one side thereof by the printing unit.