To provide a three-dimensional base isolation device capable of avoiding application of the over-assumed seismic force to a base isolation object, and flexibly and easily changing the weight of a base isolation unit.

Application of any excessive seismic force to a base isolation object is prevented after ensuring the stability of the base isolation object in a normal state so that the initial rigidity of high restoration force is ensured in a range of small displacement when the base isolation object is displaced from the reference position in an arbitrary direction, and the magnitude of the restoration force is substantially constant when the displacement exceeds the small displacement. Further, by connecting a vertical base isolation device to a base isolation unit via a transmission, the magnitude of the restoration force can be easily adjusted and the supporting load can be easily increased when the weight of the base isolation is changed.