An electric motor vehicle main circuit system includes an AC-DC switching circuit switching a supply destination of electric power according to a type of supplied power from an overhead wire, a transformer, a tap changer switching tap positions of the transformer, a CNV converting an output of the tap changer into a direct-current voltage, an AC contactor opening and closing a power supply path between the tap changer and the CNV, an FC accumulating an output of the CNV or the overhead wire, a CH stepping up an output of the FC, an FC accumulating an output of the CH, an INV converting an output of the FC into a desired alternating-current voltage, a DC contactor opening and closing a power supply path between the AC-DC switching circuit and the CH, and a control section controlling the tap changer, the AC contactor, the DC contactor, the CNV, and the CH.