A high-voltage DC circuit breaker, comprising: a mechanical switch adapted to be installed on a DC line; an L/C circuit including a capacitor and a reactor connected in parallel with the mechanical switch, and connected in series with each other so as to cause LC resonance; a first semiconductor switch connected in series with the L/C circuit and configured to switch a flow of current in one direction; a second semiconductor switch connected in parallel with the first semiconductor switch and configured to switch a flow of current in a direction opposite the one direction; and a charging resistor connected between the junction of the L/C circuit and the first semiconductor switch and a ground to charge a voltage (+Vc) in the capacitor, wherein, in a steady state, the first and second semiconductor switches (130 and 140) are turned off, and current flowing through the line is supplied to the capacitor, thus enabling an initial voltage (+Vc) to be charged in the capacitor, wherein, when a fault occurs on a first side of the DC line, the mechanical switch is opened, and the first semiconductor switch is turned on in a state in which the second semiconductor switch is turned off, so that current flows through an arc formed in the mechanical switch and the first semiconductor switch using the initial voltage (+Vc) charged in the capacitor, thus enabling a polarity-reversed voltage (-Vc) to be charged in the capacitor via LC resonance, wherein, when the polarity-reversed voltage (-Vc) is charged in the capacitor, the first semiconductor switch is turned off and the second semiconductor switch is turned on, so that current depending on the polarity-reversed voltage (-Vc) is supplied to the mechanical switch through the second semiconductor switch, and zero current is realized in the mechanical switch using the supplied current, thus extinguishing the arc. a mechanical switch adapted to be installed on a DC line; an L/C circuit including a capacitor and a reactor connected in parallel with the mechanical switch, and connected in series with each other so as to cause LC resonance; a first semiconductor switch connected in series with the L/C circuit and configured to switch a flow of current in one direction; a second semiconductor switch connected in parallel with the first semiconductor switch and configured to switch a flow of current in a direction opposite the one direction; and a charging resistor connected between the junction of the L/C circuit and the first semiconductor switch and a ground to charge a voltage (+Vc) in the capacitor, wherein, in a steady state, the first and second semiconductor switches (130 and 140) are turned off, and current flowing through the line is supplied to the capacitor, thus enabling an initial voltage (+Vc) to be charged in the capacitor, wherein, when a fault occurs on a first side of the DC line, the mechanical switch is opened, and the first semiconductor switch is turned on in a state in which the second semiconductor switch is turned off, so that current flows through an arc formed in the mechanical switch and the first semiconductor switch using the initial voltage (+Vc) charged in the capacitor, thus enabling a polarity-reversed voltage (-Vc) to be charged in the capacitor via LC resonance, wherein, when the polarity-reversed voltage (-Vc) is charged in the capacitor, the first semiconductor switch is turned off and the second semiconductor switch is turned on, so that current depending on the polarity-reversed voltage (-Vc) is supplied to the mechanical switch through the second semiconductor switch, and zero current is realized in the mechanical switch using the supplied current, thus extinguishing the arc.