To stably hold a placing object at rest in a small-scale earthquake or the like, and to alleviate effect on the placing object in an earthquake of a medium-scale or above.

A base isolation device is provided which has a lower side plate-like member 13 fixed on a floor surface side, an upper side plate-like member 11 on which the placing object is fixed, and three or more projected members of same height, fixed to an opposed surface side of the lower side plate-like member 13 or the upper side plate-like member 11. For the projected member, a head of a round head screw 12 having a grove for a cross slot screwdriver can be favorably used. Static frictional force acts in respective contact part 14 according to a static friction coefficient of the head of the respective screw 12 and the upper side plate-like member 11, and thus the position of the upper side plate-like member 11 is not changed in a case of a small-scale earthquake or the like. Meanwhile, in a case of a medium-scale earthquake or the like, the upper side plate-like member 11 slides to alleviate effects on the placing object. During vibration, dynamic frictional force acts in the respective contact part 14, and thus excessive movement of the upper side plate-like member 11 and the placing object due to inertia can be suppressed.