To solve the problem that in order to carry out authentication of outputting print data, it is necessary to use a memory medium storing authentication information of a mobile information device, the print data or a user so that the structure may be complicated and the management of the mobile information device or the memory medium has to be managed.

At a host PC 1 side, an operational sequence of operation keys 112-114 in an operation section 105 of an image forming apparatus is designated by means of a UI of a printer driver 11 before print data is transmitted. Only when the operation keys 112-114 are operated in the designated operational sequence at the image forming apparatus, the printing authentication for printing the print data is set. At the image forming apparatus, in the case where the printing authentication is set to the received print data, only when the keys 112-114 in the operation section 105 designated by the printing authentication data are operated in the designated operational sequence, the print data is printed.