To provide a method for evaluating more precisely and simply than before the equivalent sharing velocity of the improved foundation corresponding to improvement geometry.

The method for evaluating seismic response of building is performed as follows: a seismic response of building on the original foundation is obtained (S1); whether the response of the building is less than the designed value or not is checked (S2); if less than the designed value, detail design is performed on the original foundation (S3); if exceeding the designed value, improved geometry, rate of improving of the foundation, and strength of the improved foundation are set (S4); an equivalent sharing wave velocity VH of the improved foundation is calculated by using previously prepared equivalent sharing velocity graph (S5); and the seismic response of the building on the improved foundation is obtained (S6). It is checked whether response of the building is less than the designed value or not (S7); if less than the designed value, the detail design of the building on the improved foundation is performed (S8); if the response of the building is exceeding the designed value, improved geography, rate of improving of the foundation and the strength of the improved foundation are set again (S4); and steps following to the S5 are performed again.