To maintain earthquake energy absorption by a buffering area for a long period while harmful influence such as collapse of peripheral ground, ground settlement or secular deterioration of a buffering material is previously prevented.

The base isolation structure of a structure concerning the invention is composed of a support body 5 providing a dynamic soil pressure buffering area 4 among an underground outer wall 2, a pile 7 and a peripheral ground 3 being the underground buried part of the structure 1 and supporting the dynamic soil pressure buffering area by soil pressure from the peripheral ground 3, and a dynamic soil pressure buffering material 6 disposed on the inside of the support body. The support body 5 is composed so that static soil pressure at the normal time and dynamic soil pressure at the time of an intermediate or small earthquake are supported, and it is at low strength of a degree broken by the dynamic soil pressure for a constant scale or more earthquake. The dynamic soil pressure buffering material 6 is disposed in the inside of the support body 5 in a state where it is filled into a non-expansion and contraction bag body 9 together with air, and when the support body 5 is broken and dynamic soil pressure is directly acted, the dynamic soil pressure is composed to be absorbed by viscosity damping at the time when the dynamic soil pressure buffering material 6 fluidizes in the bag body 9.