The surface SH waves technique has been used to evaluate the fatigue cracks at the surface of mild steel specimens. In this study, the diffraction of surface SH waves received by double-probe technique was used. Firstly, the specimens introduced surface slit were inspected. With the results that the amplitude decreased and the propagation time increased with the slit depth. Secondly, the length and the depth of the fatigue cracks, which initiated at a small drill hole by rotating-bending fatigue, were evaluated with the difference between the propagation time of the inspected plate with crack. With the results that the evaluation of the crack growth behavior showed good agreement with measured values.