A gas turbine rotor includes: a first rotor in a shaft shape extending by a predetermined length in an axial direction, and provided with an insertion hole at an end of the first rotor; a second rotor in a shaft shape extending by a predetermined length in the axial direction, and provided with an insertion part extending by a predetermined length at an end of the second rotor and corresponding to the insertion hole such that the insertion part is inserted into the insertion hole; and a connecting member mounted between the insertion hole and the insertion part to connect the first rotor and the second rotor together, and made of a material having a thermal expansion coefficient different from a thermal expansion coefficient of both the first rotor and the second rotor.