To increase heat transfer by impingement cooling air by providing an outside face facing combustion gas and the opposite inside face cooled by impingement air and arranging a plurality of mutually adjacent ridges and grooves on the inside face.

A stator blade 22, formed of a surrounding wall 28 shaping the blade, is provided with an outside face 30 defining a substantially concave-shaped positive pressure side face, on which combustion gas 20 flows during operation, and a substantially convex-shaped negative pressure side face on the opposite side. On the opposite side to the outside face 30, the blade wall 28 is provided with an inside face 40 defining a radially extending internal passage or a hollow 42 which extends along the blade width axial line 32 for passing cooling air 16. On the stator blade inside face 40, a plurality of ridges 44 and grooves 46 are formed adjacently mutually and in parallel to each other, so that a surface area usable for cooling by the cooling air 16 can be increased without any great pressure loss of the cooling air 16. The stator blade 22 is heated from the outside by means of combustion gas 20 flowing on its surface, while the cooling air 16 fed to the inside of the stator blade 22 extracts additional heat from the large surface area of the blade wall 28, and consequently, cooling of the stator blade 22 during the operation can be improved.