A turbine rotor unit and a method of producing the same are disclosed. This turbine rotor unit comprises a ceramic rotor, a ceramic shaft integrally united with the ceramic rotor and a metal shaft provided with a cylindrical portion fixing the ceramic shaft therein and is characterized by having a gap between a substantial portion of the inner peripheral surface of the cylinder portion located near the side of the ceramic rotor and the outer surface of the ceramic shaft. Further, the turbine rotor unit is produced by arranging on one end of the metal shaft a cylindrical portion wherein an inner diameter at its opening side is larger than that at the bottom side, inserting the ceramic shaft into the cylindrical portion, and fixing the ceramic shaft to the cylindrical portion at its small diameter side.