To provide a seismic isolator which reliably reduces shake in any direction due to an earthquake and returns to an initial position with a simple structure.

In a seismic isolator S, a seismic isolation mechanism 30 is provided between a bottom plate 10 and an upper plate 20. The seismic isolation mechanism 30 has: a middle plate 40 arranged between the bottom plate 10 and the upper plate 20; a center ring 50 fixed to the bottom plate 10 and the upper plate 20 toward the middle plate 40; a plurality of circle pins 60 arranged at positions in an outer circumferential side of the center ring 50 separated from the middle plate 40 by a specified interval; and a plurality of spring members 70 engaged with each of circle pins 60 and energized toward the center ring 50. When the center ring 50 is at an initial position, an energizing force of the center ring 50 through the spring members 70 presses with the same energizing force, and the center ring 50 fixed to the bottom plate 10 relatively slides along a plane of the middle plate 40 against the spring members 70.