In a turbine blade in which a tabular rib partitioning the blade into a pressure side and a suction side is provided in substantially the midsection of the blade along a center line connecting a leading edge and a trailing edge, and at least two cavities of which a cavity at the suction side and a cavity at the pressure side do not communicate with each other are provided, a pressure adjustment member for cooling air flowing into and out of the cavity at the suction side reduces the amount of cooling air flowing into the suction side, relative to the pressure side.