In order to investigate crack propagation behavior of thermal fatigue on the basis of non-linear fracture mechanics, crack propagation tests were conducted for isothermal fatigue at several temperatures and for cyclic temperature fatigue. The results obtained were summarized as follows. (1) The fracture mechanics laws in isothermal fatigue dl/dN-ΔJ_f and dl/dN-ΔJ_c relations where dl/dN was crack propagation rate, ΔJ_f was fatigue J-integral range and was ΔJ_c was creep J-integral range) showed little dependence on temperature. (2) A simple evaluation method of the values of ΔJ_f and ΔJ_c in thermal fatigue was proposed. (3) Crack propagation under cyclic temperature could be divided into two types which were cycle-dependent and time-dependent. dl/dN had good correlations with ΔJ_f and ΔJ_c for each type, respectively. (4) The transient condition between two types was given by a function of ΔJ_f and ΔJ_c. (5) The same fracture mechanics laws were obtained in isothermal and cyclic temperature fatigue.