This paper deals with evaluation of singular stress field for V-shaped notch specimen by using the small crack problem. In this study, a stress intensity factor of small crack at V-shaped sharp notch is analyzed by the crack tip stress method. The dimensionless stress intensity factor of small crack, normalized by the intensity of V-shaped notch without the crack, is independent of the notch depth and the loading conditions. By applying the evaluation of fracture strength for V-shaped notch specimen, it is found that the fracture toughness K_<IC> of small crack problem is almost constant independent of the notch depth and the loading conditions.