The reinforced building structure which is lightweight, and working efficiency is preferable, and has a fire preventive performance and a decay durability, and can improve earthquake resistance strength without relying bracing. The structural building frame includes a pair of columns placed at facing in right and left, the upper horizontal member and the lower horizontal member jointed to each columns. The predetermined size of fiber reinforced cement siding 9 is installed in the structural building frame by horizontal boarding, and is fastens by nail 4 or screw by predetermined spacing.