Even in case of using a hand-held personal computer, operability regarding a printing operation is improved and a print can be normally completed without allowing the print to be finished as an error. When a sufficient available area exists in an RAM 11 of a hand-held personal computer 1, image data sent from an application is converted into print data and, thereafter, the print data is temporarily stored as a spool file into the RAM 11. At the point when the whole print data is stored and the spool file is completed, a printing process in the application is released and the print data in the spool file is sent to a printer 5 by a background. If the sufficient available area does not exist in the RAM 11 of the hand-held PC 1, the whole print data is not temporarily stored as a spool file but the raster unit image data sent from the application is converted into the print data. The print data is sequentially sent to the printer 5 by the foreground and the printing process is executed.