A sheet size determining portion determines, upon start of execution of a print job, whether or not a sheet size corresponding to raster image data to be printed in the print job matches a sheet size of a sheet conveyed in the print job. A size error detecting portion determines, in a case where the sheet size corresponding to the raster image data does not match the sheet size of the sheet, whether or not a print pixel to be printed exists in an excess region of the raster image data that is outside the sheet size of the sheet. A printing portion continues execution of the print job in a case where no print pixel exists in the excess region and stops the print job in a case where the print pixel exists in the excess region.