We have performed an experiment aimed at developing a high power ultrasonic motor based on a thin, lightweight, travelling-wave type design. This paper presents a detailed analysis of experimental results. Three prototype motors of the improved type were fabricated, having outer diameters of 50, 70 and 90 mm. Compared to a motor employing a piezoelectric element of the same outer diameter and the same resistive resin material as conventional types of motors, approximately twice as high maximum torque and four times as high maximum output power have been obtained with the prototype motors. It has also been confirmed that these motors have sufficient durability to withstand high-loads.