To provide excellent base isolation performance even under high surface pressure by restraining deformation of rigid plates of rigid plate layers at earthquake occuring time to a base isolation device having an upper plate having a downward projecting level different part on an under surface, a lower plate having an upward projecting level different part on an upper surface so as to be opposed to the lower side of the level different part of this upper plate and a laminated part alternately laminating rubber-like elastic layers and the rigid plate layers in the vertical direction, being the rubber-like elastic layers in both the uppermost part and the lowest part and being respectively fixed to the respective level different parts of the upper plate and the lower plate.

The whole periphery of an outer peripheral surface of respective level different parts 1a, 2a of an upper plate 1 and a lower plate 2 is positioned on the horizontal directional outside separate by 2.5 times or more of a thickness (t) in respective rubber-like elastic layers 6 of the uppermost part and the lowest part of a laminated part 5 to an outer peripheral surface of rigid plate layers 7 of the laminated part 5.