In a printing system in which with a plurality of different types of controllers connected to one serial bus, different types of print data can be inputted to and printed by a printing unit. When a set top box and desktop and portable personal computers, different in type from each other, are connected to a IEEE 1394 serial bus, screen data is outputted from the set top box to an AV/C printer and PDL data is outputted from the personal computers to the AV/C printer. The AV/C printer judges the image type of the input data. Based on the image type, the printing system converts the print data to a type of print data supported by the AV/C printer.