A representative roof frame structure incorporates: paired wood sloping beams respectively extending from a ridge portion toward eaves on opposite sides from each other; a hanging portion hanging vertically downward from the ridge portion; and two steel braces respectively installed between lower faces of the sloping beams and side faces of a lower end of the hanging portion, wherein one end of each of the steel braces is pin-jointed to a beam-side fixing portion protruding from the lower face of the sloping beam, and the other end of each of the steel braces is pin-jointed to a hanging-portion-side fixing portion protruding from the side face of the lower end of the hanging portion.