An electric motor car controller includes a voltage detector for detecting the voltage across a filter capacitor, an energy amount calculator for calculating the amount of energy of the filter capacitor from the output of the voltage detector, a frequency band component detector for extracting a given frequency band component included in the amount of energy, a frequency band component coefficient unit for multiplying the frequency band component by a coefficient and outputting a q-axis current command correcting value, and a q-axis current command correcting value adder for adding a q-axis current command correcting value to the q-axis current command value to correct the q-axis current command value.