To stably support a glass pane by projecting a locking piece on one side edge of a glass groove, fixing a steel slipping-out preventive member to the glass pane upper edge, and allowing the slipping-out preventive member by abutting to the locking piece.

A fireproof glass pane G is allowed to abut to the inside surface side of an upper surface part 5a of a main body part 5 constituting a slipping-out preventive member 4 on the upper edge or an end surface of the upper edge and the side edge. Next, a fixing screw 6 is screwed in and fixed to a tap hole 5c of the main body part 5 by sandwiching a shock absorbing mat arranged on a surface of the glass pane G, and afterwards, a peripheral edge part of the fireproof glass pane G is fitted via battens 1d, 2a in a groove part 10 formed on an inner peripheral surface of a frame body so that a glass bead 9 is installed and held. Even if the fireproof glass pane G hangs down by heating, the slipping-out preventive member 4 fixed to the fireproof glass pane is locked on a frame side locking piece 1a' to regulate hanging-down more than that. Thus, a required process is only to fit/support the glass pane in a glass groove of the frame body in a state of previously fixing the slipping-out preventive member to the glass pane, the working efficiency is largely improved, and the slipping-out preventive member is locked on the locking piece to reliably prevent separation of the glass pane from the glass groove.