Provided is a turbine blade structure that is capable of suppressing quality variations of cast products during the manufacturing of turbine blades. A turbine blade structure wherein the space inside an air foil is divided into a plurality of cavities, partitioned by rib members provided substantially perpendicular to the center line connecting a leading edge and a trailing edge, is provided with partition members that partition the inside of the cavities located in the central portion of the blade, excluding the blade leading-edge side and the blade trailing-edge side, into blade pressure side cavities and blade suction side cavities substantially along the center line, wherein blade leading-edge end portions and blade trailing-edge end portions of the partition members are inserted from one shroud surface side to the other shroud surface side along engagement grooves formed on the rib members.