Depth sizing of stress corrosion crack (SCC) by ultrasonic testing has been required in the inservice inspection of primary loop recirculation pipes in boiled water reactor type power stations. Crack tip diffraction techniques are used for the depth sizing, and inspectors are required their experiences and skills to identify weak crack tip diffraction echoes which are critical for accurate depth sizing. Better understanding of complicated wave propagation behavior around a crack may offer an idea to detect the weak crack tip diffraction echo effectively. In this paper, ultrasonic visualization equipment is constructed to observe how ultrasounds travel in solids, and behavior is discussed as longitudinal and shear waves strike slits or SCCs.