A preview system utilizing an operating system standard spooler for spooling intermediate data converted from print data supplied from an application, including a print processor for implementing a print thread process and a preview thread process and a previewer for executing preview based on a bit map produced based on the above described spooled intermediate data, wherein the preview thread process of the above described print processor is started in accordance with commencement of a print process to start up the above described previewer, and the print thread process of the above described print processor is started up in the case where there is any job which has already finished undergoing preview or any job which has not yet undergone preview settings.