The horizontal structural frame and the underground construction methods using it

The present invention relates to an underground building construction method using a horizontal structural frame forming a wide girder, and a horizontal structure frame applied thereto. The underground building construction method comprises steps of: a) constructing a retaining wall; b) installing a steel frame vertical member (70) underground to support construction load; performing the earthwork of a floor structure of a first structure; c) performing the earthwork of the floor structure of the first structure; d) installing a horizontal structural frame (20) of the floor structure of the first floor; e) building a slab of the floor structure of the first floor; f) completing the floor structures of underground floors by repeating step c) to step e) including the earthwork, the installation of the horizontal structural frame (20), and the construction of the slab down to the lowest floor; g) constructing the foundation of a building; and h) constructing a permanent pillar (10). The horizontal structural frame (20) installed in step d) includes: a double girder member (21); a plurality of beam members (23) or a deck plate; a bracket member (30) connecting the double girder member (21) to the permanent pillar (10), wherein the double girder member (21) having a pair of steel frame-shaped steels (22) arranged thereon to face each other in order to form an internal space (S) having the permanent pillar (10) placed therein.