It is important to clarify the effects of nonmetallic inclusions on rolling contact fatigue life to extend or to predict the life of the rolling bearings. The observation of initial cracks from internal defects is desirable from this point of view. In this study, high carbon-chromium bearing steel, SUJ2, with a number of artificial pores as internal defects was prepared. Initial cracks around pores under rolling contact were observed and the stress was CAE analyzed with the following results:rn1. The exposure of the initial crack surface by forced breaking and the subsequent fracture observation in this study were effective to identify the mode of the initial crack generation.rn2. The tensile stress around the pores initiated mode-I crack, and the pore with cracks is subjected to crack propagation process by internal stress under rolling contact fatigue.rn3. Rolling contact fatigue life is not simply dominated by the size of initial defects in steels. As observed in this study, the sum of initial defect size and rim crack size may control the fatigue life. This suggests that the inclusion types and the interfacial adhesiveness between inclusions and matrix may influence rolling contact fatigue.%正常な潤滑環境のもとで使用される転がり軸受部品の主rn要な破損形態は，転がり疲れによって部品内部に発生したrnき裂が，進展して表面に至ることで部品表面のはく離を引rnき起こす内部起点型破損であることが知られる。この転がrnり疲れによる内部起点はく離に対して，鋼の製造過程で不rn可避的に混入する非金属介在物（以下，介在物と略す）が，rnはく離の起点として作用し，転がり疲れ寿命に明らかに影rn響を及ぼしている。
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