Disclosed is an improved transfer mechanism that transfers, in a vertical heat treatment system, process objects W between a container (carrier), and a holder (boat) holding plural process objects at vertical intervals. The transfer mechanism includes plural substrate support devices spaced at intervals, and each of the substrate support devices has a gripping mechanism for gripping a process object on the under side. The gripping mechanism includes a fixed engagement member on a distal end of the substrate support device, and a movable engagement member movably attached to a proximal end of the substrate support device.