To provide a structural design method for a house constructed by a wooden framework method without depending on the skill and intuition of an engineer.

This computer program has processes for: (a) primarily determining excess/shortage of rigidity of a story from the ratio of the sum of horizontal rigidity of the story to horizontal seismic load or wind load; (b) adding rigidity by the rigidity shortage portion to a predetermined position; (c) computing seismic load and wind load imposed on structural members of each reference plane, from the rigidity including the added rigidity of the structural members of each reference plane by a calculation expression considering a torsion correction factor; (d) comparing the load imposed on the structural members of each reference plane with the allowable horizontal load of the structural members of the reference plane; (e) increasing the rigidity of the structural members in proportion to the ratio of the imposed load to the allowable horizontal load when the load imposed on the structural members in one or more reference planes exceeds the allowable horizontal load of the structural members; (f) repeating the processes until the load imposed on the structural members is not more than the allowable horizontal load of the structural members; and (g) outputting the seismic load and wind load imposed on the structural members, the allowable horizontal load and the increased rigidity.