An object of the invention is to diagnose whether an overcurrent detecting function with respect to a power semiconductor element of a power conversion apparatus is normal. The power conversion apparatus of the invention is provided with IGBTs as the power semiconductor element which performs a switching operation to convert DC power supplied from a DC power source into AC power, an overcurrent detecting circuit, and an overcurrent simulating circuit. The IGBTs include an emitter sensing terminal which outputs a sense current according to a current flowing to an emitter electrode. The overcurrent detecting circuit detects the overcurrent flowing to the IGBTs on the basis of the sense current output from the emitter sensing terminal. The overcurrent simulating circuit outputs a simulation signal which simulates the overcurrent flowing to the IGBTs and toward the overcurrent detecting circuit.