When the picture image data stored in a removable medium or a hard disc are printed or output as a file according to an order placed by a customer, output processing is carried out efficiently by an operator regardless of his/her experience. A task in which a unit of output processing is carried out is assigned to each printing material or to each kind of medium, and received order information is stored with images to be processed. Units of processing are grouped in terms of the kind of task. The image data grouped in different groups are stored in different buffers, and the image data in the same buffer are output collectively when corresponding to the same printing material or to a recording medium from each buffer, to thereby reduce the number of changes of printing materials or recording media.