To prevent trouble such as inclination of a structure and to make a device readily applicable even to existing structures.

This base isolating device absorbs and damps the vibration of an earthquake between structure support 3, such as a column, foundation, base, etc., supporting a structure such as a building, machine, equipment, or device, and a foundation 2 supporting the structure support 3, thus restraining transmission of great vibration to the structure and enhancing the earthquake resistance of the structure. In this case, the foundation 2 is made movable in a horizontal direction Y relative to the structure support 3 by forming a sliding surface 15 between the structure support 3 supporting the structure and the foundation 2 supporting the structure support 3, and a damping material 14 is packed between the peripheral surface 4 of the structure support 3 and a support frame 13 surrounding the contour of the structure support 3 and secured to the foundation 2, and the vibration in the horizontal direction X of the structure support 3 which occurs relatively when the foundation 2 is moved in the horizontal direction Y is absorbed and damped by the packed damping material 14 to restrain transmission of great vibration to the structure to enhance its earthquake resistance.