To acquire an earthquake response analyzer, an earthquake response analyzing method and an earthquake response analyzing program tailored to a behavior of an actual earthquake, and accurately analyzing an earthquake response.

When a calculation section 16 analyzes the earthquake response using at least a shearing stress of the ground as an analyzed object, a base time is a time for maximizing the corresponding stress in time series, a time is detected after the base time and an inner product of a stress vector at the time and a stress vector at the base time is predetermined value, a time is detected as a delimiter point after the detected time and the corresponding stress is minimized, and the shearing stress is derived based on the corresponding stress for a period from the detected delimiter point to the next detected delimiter point.