To obtain a printer in which operability is enhanced upon occurrence of a sheet mismatch error.

When sheet information other than that being stored in the tray of a printer is designated by print job data, the designated sheet information is registered on a substitute table and printed on a sheet stored in a specified tray. Even if a sheet of designated size and type is not present in subsequent print processing, a sheet mismatch error state is not brought about and print processing is executed. Since print processing is sustained without requiring to alter setting of the tray or to push a forced print switch for every print job data, operability is enhanced for the user.