This study evaluates the numerical modeling of thermal fatigue crack from the viewpoint of eddy current testing. Four relative small thermal fatigue cracks are artificially introduced into a type 316 stainless steel plate, and their eddy current signals were measured using a differential type plus point probe. Subsequent numerical simulations model each crack as a region with constant width, uniform conductivity and true profile shown by destructive tests. Analyzing the study together with earlier publications indicates that thermal fatigue crack should be modeled as an almost non-conductive region in a general sense, no matter what are frequency, size of crack and base material.