A turbine blade with a cooling structure, the turbine blade comprising: a root member configured to be coupled to a turbine disk; an inlet formed in the root member to introduce cooling air to the turbine blade; an airfoil coupled to the root member, the airfoil having a suction-side surface and a pressure-side surface; and an internal cooling channel disposed between the suction-side and pressure-side surfaces of the airfoil and configured to pass the cooling air throughout the airfoil from the inlet to an ejection hole formed on an upper surface of the airfoil, wherein the cooling channel includes: a first cooling channel configured to guide the cooling air introduced through the inlet to a leading edge of the airfoil of the turbine blade; a second cooling channel configured to guide the introduced cooling air so as to flow from a trailing edge of the airfoil of the turbine blade to the upper surface of the airfoil; and a third cooling channel provided between the first cooling channel and the second cooling channel and configured to circulate the introduced cooling air through an internal space of the airfoil of the turbine blade; and wherein the ejection hole includes a first ejection hole communicating with the first cooling channel and a second ejection hole communicating with the second cooling channel, and wherein, as the second ejection hole, a plurality of second ejection holes are formed on the upper surface of the airfoil of the turbine blade; characterized in that the cooling channel further includes: a plurality of branch channels extending outward from a middle portion of the airfoil branches off from the second cooling channel disposed near the upper surface of the airfoil of the turbine blade and wherein the plurality of branch channels communicate with the second ejection holes formed on the upper surface of the airfoil of the turbine blade. a root member configured to be coupled to a turbine disk; an inlet formed in the root member to introduce cooling air to the turbine blade; an airfoil coupled to the root member, the airfoil having a suction-side surface and a pressure-side surface; and an internal cooling channel disposed between the suction-side and pressure-side surfaces of the airfoil and configured to pass the cooling air throughout the airfoil from the inlet to an ejection hole formed on an upper surface of the airfoil, wherein the cooling channel includes: a first cooling channel configured to guide the cooling air introduced through the inlet to a leading edge of the airfoil of the turbine blade; a second cooling channel configured to guide the introduced cooling air so as to flow from a trailing edge of the airfoil of the turbine blade to the upper surface of the airfoil; and a third cooling channel provided between the first cooling channel and the second cooling channel and configured to circulate the introduced cooling air through an internal space of the airfoil of the turbine blade; and wherein the ejection hole includes a first ejection hole communicating with the first cooling channel and a second ejection hole communicating with the second cooling channel, and wherein, as the second ejection hole, a plurality of second ejection holes are formed on the upper surface of the airfoil of the turbine blade; a first cooling channel configured to guide the cooling air introduced through the inlet to a leading edge of the airfoil of the turbine blade; a second cooling channel configured to guide the introduced cooling air so as to flow from a trailing edge of the airfoil of the turbine blade to the upper surface of the airfoil; and a third cooling channel provided between the first cooling channel and the second cooling channel and configured to circulate the introduced cooling air through an internal space of the airfoil of the turbine blade; and wherein the ejection hole includes a first ejection hole communicating with the first cooling channel and a second ejection hole communicating with the second cooling channel, and wherein, as the second ejection hole, a plurality of second ejection holes are formed on the upper surface of the airfoil of the turbine blade; characterized in that the cooling channel further includes: a plurality of branch channels extending outward from a middle portion of the airfoil branches off from the second cooling channel disposed near the upper surface of the airfoil of the turbine blade and wherein the plurality of branch channels communicate with the second ejection holes formed on the upper surface of the airfoil of the turbine blade.