To ease congestion of a data transmission line in a system by adding a printing start time command data commanding a printing start time as attribute information and starting a printing process to image data by an output of a timer means keeping the present time in the case where the image data is processed to be printed in accordance with the attribute information.

A large-capacity nonvolatile memory device 8 is connected to an image formation apparatus 7 and a timer 9 for keeping the present time is embedded in the image formation apparatus 7. When image data are sent from a computer 1 to the image formation apparatus 7, a printing start time command data commanding a printing start time is added as an attribute information. When receiving the image data via a data transmission line 6 in a system, the image formation apparatus 7 stores the image data and printing start time command data in the memory device 8 if the printing start time command data is included. A printing command is output when the timer 9 shows the printing start time, and the data stored in the memory device 8 is deleted when the printing is completed.