To enable a flexible mode of use in terms of floor planning by ensuring a space without any diagonal members in a center span as a main part in building space planning, and shorten the construction period of and reduce the cost of steel work.

For saving labor for steel work in a rigid frame structure, all basic joints of columns and beams are jointed by pins. For the same possible section of steel materials of each floor, spans with a triangular frame are erected on opposite sides of all main frames along a span direction, and for a trapezoidal frame shape of each floor, brace parts are collectively arranged in a peripheral region, so that the frame structure ensures consideration of elimination of hindrance to building space structure.