A method that makes uniform the frame height after joining a frame and a substrate constituting the vacuum container of an image-forming apparatus without damaging the substrate surface in the vacuum container. A frame member is joined with a rear plate by applying frit glass to the rear plate, disposing a frame member on the frit glass, disposing a spacing definition member to a portion of the rear plate nearby the frame member where the vacuum container is not formed, pressurizing the frame member, and then softening the frit glass and thereby joining the frame member with the rear plate.