PURPOSE: To provide a connection structure of turbine disk in which materials of which coefficients of thermal expansion are different largely from each other can be used for turbine disk, a thermal expansion difference due to a difference in thermal expansion coefficient can be absorbed, a torque to drive a compressor can be transmitted, center dislocation is rate to be produced, and bending rigidity is high.

CONSTITUTION: A connection structure of turbine disk comprises a turbine disk 12 with multiple turbine blades 4 around its peripheral part 11a, a compressor shaft 14 connected to one end of the turbine disk and extending in its axial direction, and tie bolts 16 screwed into the compressor shaft to connect the turbine disk to the compressor shaft. Also a connection part 13 of the compressor shaft and the turbine disk comprises a multiple trapezoidal recessed grooves provided in one of them and multiple trapezoidal protruded parts provided on the other and fitted closely to the recessed grooves. Then the trapezoidal recessed grooves and trapezoidal protruded parts are made in contact with each other on two surfaces which form trapezoidal slanted surfaces and are extended in radial direction, respectively.