A turbine stator vane includes: a vane body which includes: an airfoil portion which has a serpentine flow passage inside thereof, the serpentine flow passage including a plurality of cooling flow passages and a plurality of turn-back flow passages; a shroud disposed on at least one of a tip end side or a root end side, in the vane height direction, of the airfoil portion; and a lid portion fixed to the airfoil portion. The lid portion forming the turn-back flow passage and being provided as a separate member from the airfoil portion. The lid portion has an inner wall surface width formed to be greater than the flow-passage width of the cooling passage formed in the airfoil portion, and a minimum value of a thickness of the lid portion is smaller than a thickness of a part of the shroud to which the lid portion is mounted.