A capacitor current estimating unit estimates a capacitor current based on phase currents. A capacitor temperature estimating unit estimates a capacitor temperature based on the capacitor current. A motor controller can accurately estimate not only a temperature of a switching element but also the capacitor temperature based on the phase currents. As a result, the capacitor does not need to have excessive heat characteristics. Further, a current limiting unit limits a current flowing from a battery to an inverter based on the capacitor temperature. Therefore, an amount of temperature change is not over-estimated due to overheating of the capacitor. As a result, excessive current limitation can be avoided and the performance of the motor can be demonstrated.