To provide a new structure and a construction method for a horizontal muntin material of a balustrade, which is used for a veranda and a balcony and fixed structurally by a screw.

The balustrade of the veranda, etc., is composed of an aluminum shape. The cylindrical horizontal muntin material, wherein a part between balustrade supports 1 is composed of a rod material parallel to the balustrade 3, is split into a front member 5 and a rear member 6. An intermediate rib 9 is provided in a split position of the front member 5 so as to constitute a screw receiving thick part 10, and fixed to a front surface of the support 1 via a mounting plate 11 by the screw. Characteristically, a fitting structure 16 corresponding to a fitting structure 8 constituted in the split position of the front member 5 is provided in a split position of the rear member 6, and the rear member 6 cut in a width equal in dimension to an interval between the supports 1 is fitted for integration into the front member 5 fixed to the support 1.