Shot-peening effects on the fatigue life behavior of bearing steel (JIS SUJ2) have been investigated. Hourglass-shaped test specimens were heat-treated and then surface-treated using a shot-peening machine. Results of a rotary bending fatigue test showed that shot-peening suppressed not only much of the surface-originated fracture but also the scattering error of the probabilistic stress-life data, and improved the fatigue life by about 6 times through the load levels of the cyclic tests. Such large increase in fatigue life was driven by the following reasons: The increase of hardness in the skin caused the predicted fatigue limit stress to increase by 15%; fracture-initiating inclusions were distributed at deeper locations, experiencing low nominal stresses; and the increase in the fish-eye fracture size by an average of 180%.