The present invention relates to an improvement of a turbine blade in a gas turbine and, more particularly, to a cooling structure of the turbine blade. The turbine blade comprises a hollow-structured main body (2) and cooling medium discharging device (3) located in the inner cavity of the hollow-structured main body (2) and formed to discharge a cooling medium from the surface thereof, so that the cooling medium discharged from the cooling medium discharging device (3) impinges against the inner surface of the main body (2) to remove the heat from the same. The turbine blade further includes a projection (9) which is formed on the inner surface of the leading edge (8) of the main body (2), extending along the spanwise direction of the blade, and the cooling medium discharging device are formed to allow at least part of the cooling medium to directly impinge against proximal portions of the projection (9). With this arrangement, the invention can provide a turbine blade which allows a small amount of cooling air to cool the turbine blade and its leading edge (8) in particular with great effectiveness.