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Flaking type failures in rolling contact processes are usually attributed tofatigue-induced subsurface shearing stress caused by the contact loading. Assumingsuch crack growth is due to mode II loading and that mode I growth is suppresseddue to the compressive stress field arising from the contact stress, we developed a newtesting apparatus for mode II fatigue crack growth. According to the test results onbearing steel JIS-SUJ2 and other hard steels, stable mode II fatigue crack growth wasobserved in the range of the values of the ∆KII, namely, between lower boundapproximately 3MPam and upper bound 5-10 MPam. The value of upper bounddepends on the values of superimposed compressive stress. If applied ∆KII is larger thanthis critical value, mode I (tensile mode) fatigue crack growth occurs on the plane ofmaximum tensile stress.