Abstract: A gas turbine having cooling structure disposed on an outside peripheral side in a radial direction of a movable vane in which the cooling efficiency is further improved and sealing structure disposed on an inner peripheral side to suppress leakage of sealing air and prevent invasion of combustion gas into the turbine disc and enlargement of sealing air clearance is prevented. Outwardly in the radial direction, a gap between ring segment (90) and impingement cooling plate (92) disposed on the outer periphery thereof, is divided in the axial direction by a pressure partition plate (97) extending in a circumferential direction so as to provide plural cavities adjusted to different pressures, thereby forming a cooling structure in the ring segment (90). Inside in the radial direction, a static vane inside diameter side cavity (53) and downstream cavity (31) are formed by a box (57) for sealing the static vane inside diameter side cavity (53).