There is provided a shroud structure for gas turbines capable of suppressing a drop in the amount of cooling air for cooling the inner shroud by reducing the amount of cooling air leakage that occurs along the cooling air path when feeding cooling air from the one-piece outer shroud to the inner shroud of the gas turbine and ensure more reliable cooling of the inner shroud. The gas turbine shroud structure contains a one-piece outer shroud, and an inner shroud retained on the inner circumferential side of the outer shroud in a structure divided into multiple inner shrouds along the periphery. An inner seal plate groove is formed on the outer circumference of the hook formed on the inner shroud, a seal plate is inserted in the inner seal plate groove, and the seal plate is mounted so that a section of the seal plate protrudes in the gap between the hook mechanism of the outer shroud and the inner shroud.