Strain-controlled fatigue tests using a flexural resonant vibration were performed on miniature temperatures between 293K and 573K. From the investigations of in situ changes in the resonant period , P, and in the drive force, DF, applied to the specimens during the fatigue tests, the following results were obtained.(1) Overlapped on general changes in P and DF, small and step-like changes in P and DF were fatigue damages. (2) General changes of P at the middle stage during the fatigue tests were a slight increase (softening) at T=333 K but a strong decrease (hardening) at T=573 K. From the detailed study of