A rigid building structure having a hexagonal lattice in the vertical plane and presenting an abundant variation in overall shape. The building structure having an overall shape defined by connecting a plurality of prismatic unit spaces each having a pair of end faces and a plurality of side faces at least in the horizontal direction comprises main hexagonal frames standing on each side face facing outdoors, edge beams provided at the outer edge of the upper end face of each unit space, and indoor columns provided on each side located indoors out of the opposite sides of the side face of eachunit space wherein the upper and lower sides of the main hexagonal frame are located, respectively, on the upper and lower sides of the side face, the right and left bends of the main hexagonal frameare located, respectively, on the right and left sides of the side face, and the main hexagonal frame, the edge beam and the indoor column are bonded mutually.