A direct-current circuit breaker that interrupts a direct current at a current zero point formed by superimposing an oscillating current on the direct current flowing through a direct-current line, the direct-current circuit breaker comprising: a circuit breaker unit inserted in the direct-current line; and a circuit unit connected in parallel to the circuit breaker unit to generate the oscillating current, wherein the circuit unit includes: a capacitor and a reactor connected in series to each other to generate the oscillating current; a high-speed closer connected in series to the capacitor to perform closing for forming the current zero point; and a lightning arrester to reduce an overvoltage of the capacitor, the lightning arrester being connected in parallel to the capacitor and the high-speed closer, characterized in that the circuit breaker unit and the high-speed closer are aligned in a first direction with a distance provided therebetween, the distance being equal to or longer than a spatial distance for insulation between sites having potentials different from each other, the capacitor and the lightning arrester are aligned in a second direction that is a direction intersecting the first direction with a distance provided therebetween, the distance being equal to or longer than the spatial distance for insulation between sites having potentials different from each other, and a combination of the circuit breaker unit with the high-speed closer and a combination of the capacitor with the lightning arrester are aligned in a third direction that is a direction intersecting the first direction and the second direction with a distance provided therebetween, the distance being equal to or longer than the spatial distance for insulation between sites having potentials different from each other. a circuit breaker unit inserted in the direct-current line; and a circuit unit connected in parallel to the circuit breaker unit to generate the oscillating current, wherein the circuit unit includes: a capacitor and a reactor connected in series to each other to generate the oscillating current; a high-speed closer connected in series to the capacitor to perform closing for forming the current zero point; and a lightning arrester to reduce an overvoltage of the capacitor, the lightning arrester being connected in parallel to the capacitor and the high-speed closer, characterized in that the circuit breaker unit and the high-speed closer are aligned in a first direction with a distance provided therebetween, the distance being equal to or longer than a spatial distance for insulation between sites having potentials different from each other, the capacitor and the lightning arrester are aligned in a second direction that is a direction intersecting the first direction with a distance provided therebetween, the distance being equal to or longer than the spatial distance for insulation between sites having potentials different from each other, and a combination of the circuit breaker unit with the high-speed closer and a combination of the capacitor with the lightning arrester are aligned in a third direction that is a direction intersecting the first direction and the second direction with a distance provided therebetween, the distance being equal to or longer than the spatial distance for insulation between sites having potentials different from each other. a capacitor and a reactor connected in series to each other to generate the oscillating current; a high-speed closer connected in series to the capacitor to perform closing for forming the current zero point; and a lightning arrester to reduce an overvoltage of the capacitor, the lightning arrester being connected in parallel to the capacitor and the high-speed closer, characterized in that the circuit breaker unit and the high-speed closer are aligned in a first direction with a distance provided therebetween, the distance being equal to or longer than a spatial distance for insulation between sites having potentials different from each other, the capacitor and the lightning arrester are aligned in a second direction that is a direction intersecting the first direction with a distance provided therebetween, the distance being equal to or longer than the spatial distance for insulation between sites having potentials different from each other, and a combination of the circuit breaker unit with the high-speed closer and a combination of the capacitor with the lightning arrester are aligned in a third direction that is a direction intersecting the first direction and the second direction with a distance provided therebetween, the distance being equal to or longer than the spatial distance for insulation between sites having potentials different from each other.