Abstract: Disclosed is an expansion joint apparatus comprising cover plates disposed on two bodies installed across a gap, in a manner openable by hinges, wherein each cover plate is inclined inward of the gap. The sectional shape of the two cover plates in a combined state is approximately in a V-shape. Each cover plate is thrust with a spring in a direction so that each end may approach that of the other, rotating about the hinge as the center. The angular dislocation of each cover plate is limited to the outer side of the gap, thereby always filling up the gap by opening and closing the cover plates in response to a changing gap, if the gap of two bodies should vary, because the cover plates are disposed on the bodies in a manner free to open and close.