In this study, we propose the mitigation method of a shaft voltage according to change in parasitic capacitances of a permanent magnet synchronous motor (PMSM). First, we designed the equivalent circuit taking into account all parasitic capacitances. Then, we deducted that rotor-to-winding and stator-to-rotor capacitances mainly affect the shaft voltage. The stator-to-rotor capacitance depends on the air-gap length, which directly affects output torque characteristics of the motor. In case of the rotor-to-winding capacitance, it depends on the distance from the rotor to winding, which have effects on torque ripple, but it doesn't affect average torque of the motor. Thus, rotor-to-winding capacitance is determined as a variable for mitigation of the shaft voltage. According to change in the rotor-to-winding capacitance, we obtained and compared the results of the shaft voltage, average torque, and torque ripple.