In this study rotating bending fatigue tests have been carried out with the deep non-through radial holed notch specimens of low carbon steels(SM 22C). It is investigated that the behaviors of surface and interior fatigue crack propagation and the variations of the shape of the cracked surface on the magnitude of bending stresses. The Obtained results are summarized as follows. (1) The relations between [Crack length] and [Cycle ratio] are expressed by following eq. in the 0.1~0.6 range of N/ $N_{f}$ long[ crack length] = A + B [N/ $N_{f}$ ] In case of surface crack length, values of A and B are uniformed independent upon the magnitude of bending stress, but those are variable according to the magnitude of bending stress for interior crack length. (2) The following eq. is derived on the surface crack propagation rate, bending stress and surface crack length. (dl/dN)=(3.94*10$^{-12}$ ).sigma.$^{4.54}$l (3) Under small stress, interior crack propagation rate increase with the interior crack growth but it decrease for large stress. (4) The shape of cracked surface depends upon the magnitude of bending stress. Under small stress fatigue crack propagates as an semi-ellipse with semi-major axis of surface crack length with semi-major axis of interior crack length for large stress.s.