A pole-number-changing rotary electric machine includes: a rotary electric machine; an n-group inverter; and a control unit for controlling the n-group inverter, wherein the control unit controls current phases of a current flowing through stator coils such that a current phase degree of freedom, which is a number of current phases per pole pair controllable by the n-group inverter, is equal to a number of groups n×a number of phases m/2 at a time of high polarity driving and the number of groups n×the number of phases m at a time of low polarity driving, where the number of groups n is a multiple of 4 and the number of phases m is a natural number of 3 or more and relatively prime to the number of groups n.