The technique of the invention attains a practical printing system between arbitrary clients and printers connecting with a network.An intermediation server connecting with the network is interposed between the clients and the printers to intermediate printing. Each client sends a printing request, which includes selection of print data and specification of a printer as an output destination, to the intermediation server. The intermediation server converts the selected print data into a general purpose format, which does not depend upon the type of the printer, and transfers the converted print data to the specified printer.