The present invention relates to a gas turbine cooled moving blade in order to cool the gas turbine using steam alone. In the moving blade, two cavities are installed in the lower part of the moving blade root section of the moving blade, a steam inlet is located in one cavity, and a steam outlet is installed in the other cavity. Steam is charged from the steam inlet and passes through a serpentine cooling passage consisting of a plurality of steam passages, and discharged to the steam outlet and collected. Bypasses are located near the base of the moving blade in the middle of each steam passage, so that cold steam on the leading edge side can be led into the bypass, mixed with the hot steam which comes from the tip section side and goes into the next downstream section of the steam passage, and flows to an upstream portion of the steam passage, thereby equalizing the steam temperature and cooling the steam over the entire range from the upstream to downstream of the steam flow. A turbulator is installed in the middle of steam passage in order to generate turbulence and enhance heat transfer. Since the moving blade is evenly cooled by steam alone without using air, and the steam is then collected, the performance of the gas turbine can be enhanced.