To provide an earthquake tremor reducing apparatus capable of accurately cutting off or attenuating external force caused by a large earthquake not only when a supported body is in normal operation or an earthquake is a normal magnitude, but also when a large earthquake occurs in a state that a heavy suspended object or a target placed on a floor is supported.

An expandable earthquake tremor reducing apparatus 10 allowed to be expanded/contracted between a supporting body 100 and a supported body 200, and when receiving external force, reducing overload applied to the supporting body 100 is configured so that not only a coil spring 400 is arranged between opposite faces of a seat plate 120 attached on the side of the supporting body 100 and a seated plate 220 attached on the side of the supported body 200 but also an earthquake tremor reducing damper 500 for reducing external force by applying compression resistance against such overload that a space between the opposite faces of the seat plate 120 and the seated plate 220 is narrowed is arranged between the opposite faces.