To provide an expansion joint structure having no member broken by an earthquake.

Elastically displaceable an elastic member 11 in a horizontal direction is normally arranged in a compressed state between a stepped vertical face 31a formed on the ground 3 and an end face 21a of an overhang part 21 of a base-isolated building 2. Even when a distance between the stepped vertical face 31a and the end face 21a becomes larger than normal in case of an earthquake, the elastic member 11 is in contact with the stepped vertical face 31a and the end face 21a. When the distance between the stepped vertical face 31a and the end face 21a becomes shorter than normal, the elastic member 11 is further compressed than normal by the stepped vertical face 31a and the end face 21a.