A controller of a rotating electric machine includes a current detector detecting a voltage of each of shunt resistors in at least two phases from among the shunt resistors in three phases during an electric current flowing period in which the shunt resistors in the at least two phases have an electric current flowing therein; and a signal generator setting a switching mode of each of switches forming an inverter for controlling an estimated angular velocity to an instruction angular velocity based on the detected voltage. The signal generator sets a switching mode to flow the electric current in the shunt resistors in the at least two phases during at least part of one half of a modulation cycle of control of the estimated angular velocity.