A power conversion device provided between a DC power supply and an AC electric path, said power conversion device being equipped with: a cutoff unit provided on at least one line in an output electric path in the power conversion device; a first voltage sensor that detects a voltage between the lines in the output electric path on the primary side of the cutoff unit; a second voltage sensor thatdetects a voltage between the lines in the output electric path on the secondary side of the cutoff unit; and a determination unit that obtains a primary-side voltage and a secondary-side voltage anda primary-side phase and a secondary-side phase on the basis of the respective detection outputs from the first voltage sensor and the second voltage sensor, and, on the basis of a phenomenon whereinthe absolute value of the voltage difference between the primary-side voltage and the secondary-side voltage is greater than a voltage difference threshold value and the absolute value of the phase difference between the primary-side phase and the secondary-side phase is greater than a phase difference threshold value, determines that the cutoff unit is open.