A turbine blade comprising: an airfoil; a supply channel extending through the interior of the airfoil in the span direction, through which cooling fluid flows in operation; an insert in the form of a substantially cylindrical member disposed at a predetermined space from the inner wall of the supply channel, wherein the insert has a plurality of discharge holes through which the cooling fluid flowing therethrough spouts against the inner walls of the supply channel for impingement cooling; a pin fin channel extending from the supply channel along the center line of the airfoil toward the trailing edge of the airfoil and opening at the trailing edge to the exterior of the airfoil, wherein the pin fin channel is a channel in the supply channel through which cooling fluid flows in operation after being used for impingement cooling and constitutes a structure related to pin fin cooling for cooling the vicinity of the trailing edge of the airfoil; a plurality of gap pin fins which are columnar members projecting from a pair of opposing inner walls that constitute the pin fin channel at a region at the supply channel side of the pin fin channel, wherein the amount of protrusion of the gap pin fins from the opposing inner walls is set such that a gap is formed between the ends of the gap pin fins, said gap extending in the span direction; and pin fins connecting the pair of opposing inner walls at a region at the trailing edge side of the pin fin channel; characterised in that an insertion portion (22;22A;22B), which is an end portion of the insert adjacent to the trailing edge of the airfoil and which is not provided with the discharge holes, is disposed in the gap to decrease the area of the channel for the cooling fluid at the region at the supply channel side of the pin fin channel. an airfoil; a supply channel extending through the interior of the airfoil in the span direction, through which cooling fluid flows in operation; an insert in the form of a substantially cylindrical member disposed at a predetermined space from the inner wall of the supply channel, wherein the insert has a plurality of discharge holes through which the cooling fluid flowing therethrough spouts against the inner walls of the supply channel for impingement cooling; a pin fin channel extending from the supply channel along the center line of the airfoil toward the trailing edge of the airfoil and opening at the trailing edge to the exterior of the airfoil, wherein the pin fin channel is a channel in the supply channel through which cooling fluid flows in operation after being used for impingement cooling and constitutes a structure related to pin fin cooling for cooling the vicinity of the trailing edge of the airfoil; a plurality of gap pin fins which are columnar members projecting from a pair of opposing inner walls that constitute the pin fin channel at a region at the supply channel side of the pin fin channel, wherein the amount of protrusion of the gap pin fins from the opposing inner walls is set such that a gap is formed between the ends of the gap pin fins, said gap extending in the span direction; and pin fins connecting the pair of opposing inner walls at a region at the trailing edge side of the pin fin channel; characterised in that an insertion portion (22;22A;22B), which is an end portion of the insert adjacent to the trailing edge of the airfoil and which is not provided with the discharge holes, is disposed in the gap to decrease the area of the channel for the cooling fluid at the region at the supply channel side of the pin fin channel.