A rotor, installable in a casing of a turbine and configured to be rotated by a flow of combustion gas and cooled by a flow of compressed air, has an improved structure to keep a tip clearance constant during operation of a gas turbine. The rotor includes a disk having an outer circumferential surface; a platform installed on the outer circumferential surface of the disk; and a blade airfoil formed on an upper surface of the platform, the blade airfoil having an airfoil end situated opposite to the platform, the airfoil end having an upstream side and a downstream side with respect to a flow direction of the combustion gas, wherein the blade airfoil is formed so that, when the rotor is installed in the casing, the downstream side of the airfoil end is closer to an inner surface of the casing than the upstream side of the airfoil end.