This paper presents an application of numerical simulation for ultrasonic guided wave in piping with elbow. A displacement field of torsion al guided waves in elbow and piping beyond elbow was computed using three-dimensional finite element models. We tried to utilize the predic ted displacement field to optimize the measurement condition or estimation of defect detectability. Experimental validation was carried our using artificial defects in elbow and beyond elbow region. Good agreement was obtained between model prediction and the experimental data.