To provide a mullion resisting large wind pressure and having excellent internal appearance.

A reinforcing material 9 is connected near the indoor section of a mullion body 5 by connecting fittings 11 and used as a mullion 12, and the reinforcing material 9 is fixed under the state, in which tension is applied extending over a floor 1 and a floor slab 2. Accordingly, the mullion resisting large wind pressure is manufactured because prestress is applied to the reinforcing material 9 and the reinforcing material 9 is difficult to be deflected, and the mullion having excellent internal appearance is prepared because the reinforcing material 9 is superposed to the mullion body 5 and is not conspicuous.