PURPOSE: To diversify opening design by forming a lattice beam of an upper chord member, lower chord member and a plurality of lattices for interconnecting the upper and lower end parts of an end plate.

CONSTITUTION: A lattice beam 1 is formed of a pair of vertical end plates 2, an upper chord member 3 interconnecting the upper end parts of the end plate 2 and a pair of lower chord members 4 and a plurality of lattices 5 extending obliquely upward from the lower end parts of the end plates 2. Rectangular plates 13 are welded to the intermediate parts of the upper and lower chord members 3, 4 to make an open ceiling 30 of a rectangular space surrounded by lattice beams 1, 25, 26. Further, an opening 32 for a gateway having the upper end located above the lower end of the end plate 2 is formed in the wall panel 11 disposed below the lattice beam 1. Thus, the limit of the height of opening design can be mitigated.