Previous researchers investigated the failures of ball surfaces of silicon nitride bearings from the viewpoint of the ring crack model. They explained the process of flaking failures in terms of surface semi-circular cracks which grew by the stresses around the circumference of the contact circle. However, contrary to their explanation, we found that the ring crack model did not explain the process of the flaking failure of plates. In the present work we compare the growth directions of surface and subsurface cracks in order to find out which crack is more dominant in the process of the flaking failure. We carried out reciprocating-rolling contact fatigue (RCF) tests and concluded that the directions of arcs formed by the semi-circular surface cracks were dominated by subsurface crack growth direction.