To provide a system for directly identifying rigidity of elastic support from vibration tests in the state that a vibration source is as loaded on the base body via the elastic support in a structure that the vibration source is elastically supported on the base body with the elastic support.

In a system for identifying the rigidity of an elastic support (mount) which elastically supports a vibration source (outboard motor) on the base body (ship's hull), the elastic support is modeled with spring rigidity and a theoretical rigidity value when the rigidity value of the elastic support is unknown is calculated from an equation of balance of force (S10 to S14). From a vibration test performed in the state the vibration source is loaded on the base body via the elastic supprot, a modal parameter in mode analysis is calculated by a curve fitting (S16, S18), an experimental rigidity value is calculated from the calculated value (S20) and based on the calculated two rigidity values, the rigidy of the elastic support is identified (S22).