An electric power conversion system includes: a primary conversion circuit; a secondary conversion circuit magnetically coupled to the primary conversion circuit via a transformer; and a failure detection unit configured to detect a failure of any one of switching elements by causing each of the switching elements to switch between an on state and an off state. The switching elements constitute a full-bridge circuit of a conversion circuit to which input voltage is supplied from a corresponding one of center taps of the transformer. The full-bridge circuit is one of a primary full-bridge circuit of the primary conversion circuit and a secondary full-bridge circuit of the secondary conversion circuit.