To provide a seismic isolator which prevents movable shelves from colliding with a stopper provided at the end of a rail by absorbing shaking energy of an earthquake in the plurality of movable shelves provided side by side on the rail.

An air damper 8 is arranged at the end of the rail 2, and a roller 7 rolling on the rail 2 is pivoted at the tip end of the piston rod 8a of the air damper 8. The roller 7 is made to bite into a wedge-shaped space between the wheel 4 of a movable shelf 3 moving toward the end side of the rail 2 in occurrence of the earthquake and the upper face of the rail 2 to retreat while braking the rotating torque of the wheel 4.