A turbine blade, comprising: a blade body having a hollow shape; a cavity provided in the interior of the blade body; and a cooling passage that is open from the cavity to a rear end portion of the blade body, the rear end portion being on a downstream side in the flow direction of the flow direction of a combustion gas in the mounted state of the turbine blade, wherein the cooling passage includes a first passage, a second passage and a third passage, each of the first, second and third passages being partitioned by a pressure-side wall portion and a suction-side wall portion forming the blade body, the first, second and third passages defining a flow direction for cooling air from the cavity to the rear end portion of the blade body, wherein the first passage has a base end portion communicating with the cavity and a tip portion extending toward the rear end portion of the blade body, the first passage having a width between the pressure-side wall portion and the suction-side wall portion that becomes narrower from its base end portion toward the rear end portion of the blade body, wherein a plurality of cooling pins are provided at predetermined intervals in the first passage, the second passage has a base end portion communicating with the first passage and a tip portion extending toward the rear end portion of the blade body, the second passage having a constant width between the pressure-side wall portion and the suction-side wall portion from its base end portion toward the rear end portion of the blade body, wherein the second passage has a nozzle cooling structure formed by a plurality of pedestals having a column shape at predetermined intervals along a longitudinal direction of the blade body, the third passage has a base end portion communicating with the second passage and a tip portion opening at the rear end portion of the blade body, the third passage having a constant width between the pressure-side wall portion and the suction-side wall portion from its base end portion toward the rear end portion of the blade body characterised in that side surfaces of each of the pedestals facing the adjacent pedestals are flat surfaces along the flow direction of the cooling air. a blade body having a hollow shape; a cavity provided in the interior of the blade body; and a cooling passage that is open from the cavity to a rear end portion of the blade body, the rear end portion being on a downstream side in the flow direction of the flow direction of a combustion gas in the mounted state of the turbine blade, wherein the cooling passage includes a first passage, a second passage and a third passage, each of the first, second and third passages being partitioned by a pressure-side wall portion and a suction-side wall portion forming the blade body, the first, second and third passages defining a flow direction for cooling air from the cavity to the rear end portion of the blade body, wherein the first passage has a base end portion communicating with the cavity and a tip portion extending toward the rear end portion of the blade body, the first passage having a width between the pressure-side wall portion and the suction-side wall portion that becomes narrower from its base end portion toward the rear end portion of the blade body, wherein a plurality of cooling pins are provided at predetermined intervals in the first passage, the second passage has a base end portion communicating with the first passage and a tip portion extending toward the rear end portion of the blade body, the second passage having a constant width between the pressure-side wall portion and the suction-side wall portion from its base end portion toward the rear end portion of the blade body, wherein the second passage has a nozzle cooling structure formed by a plurality of pedestals having a column shape at predetermined intervals along a longitudinal direction of the blade body, the third passage has a base end portion communicating with the second passage and a tip portion opening at the rear end portion of the blade body, the third passage having a constant width between the pressure-side wall portion and the suction-side wall portion from its base end portion toward the rear end portion of the blade body characterised in that side surfaces of each of the pedestals facing the adjacent pedestals are flat surfaces along the flow direction of the cooling air.