PURPOSE: To prevent any damage on a blade part from being generated by foreign matters so as to improve durability by setting the minimum wall thickness of the blade top end part on a gas inlet side with a specified relational expression from the breaking tenacity value of the blade part against the peripheral speed of the blade top end part on the gas inlet side, the weight of foreign matters which come flying while being mixed in exhaust gas, and the like.

CONSTITUTION: In a ceramic radial turbine rotor 1, a blade part 2 which consists of silicone nitride sintered body is provided on the outer circumference of a cone shaped hub part 5, and a wall thickness (t) is given to the blade top end part 4 on a gas inlet side 3. The minimum wall thickness (t) is set to t≥3.02-0.292KIC (provided that KIC is set to 4.3MPm1/2 or more) by the minimum low peripheral speed for practical use of the blade top end part 4 and the breaking tenacity value KIC of a blade part 2 under condition of the real minimum weight of foreign matters which come flying while being mixed in exhaust gas so as to be liable to break the blade top end part 4. It is thus possible to provide the turbine rotor 1 having good uniformity and durability in which any damage on the blade part 2 caused by the foreign matters may not take place.