A method of controlling discharge of printed sheets, which makes it possible to acquire a desired number of printed sheets as a sheet bundle. A controller determines whether or not printed sheets are stored in the stacker. The controller detects the number of printed sheets stored in the stacker. A controller causes the stored printed sheets to be discharged from the stacker as a sheet bundle when the number of printed sheets stored in the stacker is equal to a desired sheet count set by a user. In a case where the set desired sheet count has been changed, if it is determined that the printed sheets are stored in the stacker, the controller causes the printed sheets stored in the sheet discharge unit to be discharged from the stacker.
