In the present study, I investigate the effects of shaft vibration on asymmetric cavitation, which is one of the instability phenomena on cavitating 3-bladed inducers. Inducer tests under various unbalance conditions are performed to clarify the effects of shaft vibration. The following results are obtained. (1) The amplitude of shaft vibration has a strong effect on the occurrence of asymmetric cavitation, and in an inducer with a large vibration amplitude, asymmetric cavitation easily occurs. (2) The phase of the small-tip clearance caused by shaft vibration coincides with the position of the small cavity. In this study, it is shown that suppression of shaft vibration amplitude is extremely important in preventing harmful asymmetric cavitation.