An MMC includes arms configured with one unit converter or a plurality of cells connected in series. The main circuit of the cell includes a switching element and a DC capacitor. The power supply of the cell lowers voltage of the DC capacitor to generate power supply voltage to be supplied to the control circuit of the cell. The power supply includes a power supply circuit configured to convert input voltage provided between first and second input terminals from the DC capacitor into power supply voltage, a thyristor connected between the first and second input terminals electrically in parallel with the power supply circuit, a current-limiting resistor connected between terminals of the DC capacitor electrically in series with the thyristor, and a control unit configured to fire the thyristor when input voltage applied to the power supply circuit exceeds a threshold voltage.