A nuclear reactor vessel structure includes an inner peripheral tube-shaped steel plate, an outer peripheral tube-shaped steel plate, and an intermediate tube-shaped steel plate disposed between the inner and outer peripheral tube-shaped steel plates, and is configured to support a nuclear reactor vessel on the inner peripheral side of a tube-shaped structure with concrete placed between the steel plates. The nuclear reactor vessel structure includes a support having a tube-shaped plate disposed on the inner peripheral side of the intermediate tube-shaped steel plate, and an annular plate which protrudes to the inner peripheral side of the tube-shaped plate and to which a connection section is affixed. The support is affixed to the concrete, which is placed between the inner peripheral and the intermediate tube-shaped steel plates, by first bar members, and the support is also affixed to the inner peripheral tube-shaped steel plate by second bar members.