An electric-power converter includes a plurality of direct-current power supplies, a plurality of power conversion circuits provided corresponding to the respective direct-current power supplies, an alternating-current power system configured to cause a plurality of alternating-current ends provided in the respective power conversion circuits to be directly connected in parallel through a parallel connection point, and to supply the alternating-current power output from the plurality of alternating-current ends to an alternating-current side through the parallel connection point, a plurality of grounding wires each configured to connect at least two of a plurality of direct-current negative buses between the plurality of direct-current power supplies and the plurality of power conversion circuits, to earth, and a plurality of diodes inserted in series into the respective grounding wires, and each including a cathode side connected to the corresponding direct-current negative bus and an anode side grounded.