A turbine rotor comprises: a first member that has a cylindrical shape and extends in an axial direction of the turbine rotor, and a second member that has a cylindrical shape and extends in the axial direction of the turbine rotor, the second member being axially connected to the first member in a state in which one cylindrical end portion of the first member and one cylindrical end portion of the second member are in contact at a border, wherein a groove portion for welding is formed at the border between the first and second members by combining a first recessed portion formed by cutting one edge of an edge portion of the first member in the radial direction and a second recessed portion formed by cutting one edge of an edge portion of the second member in the radial direction, wherein a welding portion is formed which connects the first member and the second member, the welding portion being formed by performing welding at the border between the first member and the second member, characterized in that a gas-introducing hole that is for introducing inert gas into a cavity portion formed inside the turbine rotor and that penetrates a bottom portion of the groove portion at its center position is covered by welding, wherein the gas-introducing hole is covered by melting the surrounding area of the gas-introducing hole close to the border at the time of the welding at the border between the first member and the second member, the material of the first member is different with that of the second member in terms of hardness, and the second member that is lower in hardness than the first member is formed to have a length of the second recessed portion in the axial direction that is longer than a length of the first recessed portion of the first member in the axial direction, and wherein the gas-introducing hole is formed at a position away from the border between the first and second members by penetrating the second member. a first member that has a cylindrical shape and extends in an axial direction of the turbine rotor, and a second member that has a cylindrical shape and extends in the axial direction of the turbine rotor, the second member being axially connected to the first member in a state in which one cylindrical end portion of the first member and one cylindrical end portion of the second member are in contact at a border, wherein a groove portion for welding is formed at the border between the first and second members by combining a first recessed portion formed by cutting one edge of an edge portion of the first member in the radial direction and a second recessed portion formed by cutting one edge of an edge portion of the second member in the radial direction, wherein a welding portion is formed which connects the first member and the second member, the welding portion being formed by performing welding at the border between the first member and the second member, characterized in that a gas-introducing hole that is for introducing inert gas into a cavity portion formed inside the turbine rotor and that penetrates a bottom portion of the groove portion at its center position is covered by welding, wherein the gas-introducing hole is covered by melting the surrounding area of the gas-introducing hole close to the border at the time of the welding at the border between the first member and the second member, the material of the first member is different with that of the second member in terms of hardness, and the second member that is lower in hardness than the first member is formed to have a length of the second recessed portion in the axial direction that is longer than a length of the first recessed portion of the first member in the axial direction, and wherein the gas-introducing hole is formed at a position away from the border between the first and second members by penetrating the second member.