An arc detection apparatus that is applied to a DC power system, the DC power system including: a first DC power source that generates electric power or performs charging/ discharging; a DC-DC conversion circuit that converts an output voltage of the first DC power source; a load apparatus that consumes or converts an output power of the DC-DC conversion circuit; a pair of first power lines (17a, 18a) that connect the first DC power source and the DC-DC conversion circuit; and a pair of second power lines (17b, 18b) that connect the DC-DC conversion circuit and the load apparatus, characterized in that the arc detection apparatus comprises: a first capacitor whose one end portion is connected to one of the pair of first power lines, and whose other end portion is connected to one of the pair of second power lines; an electric current measurement unit that measures an electric current in the second power lines (17b, 18b); and an arc determination unit that determines whether or not an arc is generated based on a high frequency component of an alternating current measured by the electric current measurement unit, wherein an impedance of the first capacitor satisfies a condition that a combined impedance of the impedance of the first capacitor, impedances of the DC-DC conversion circuit between the pair of first power lines (17a, 18a) and the pair of second power lines (17b, 18b), an impedance of the DC-DC conversion circuit between the pair of second power lines (17b, 18b), and an impedance of the load apparatus is smaller than an impedance of the DC-DC conversion circuit between the pair of first power lines (17a, 18a). a first DC power source that generates electric power or performs charging/ discharging; a DC-DC conversion circuit that converts an output voltage of the first DC power source; a load apparatus that consumes or converts an output power of the DC-DC conversion circuit; a pair of first power lines (17a, 18a) that connect the first DC power source and the DC-DC conversion circuit; and a pair of second power lines (17b, 18b) that connect the DC-DC conversion circuit and the load apparatus, characterized in that the arc detection apparatus comprises: a first capacitor whose one end portion is connected to one of the pair of first power lines, and whose other end portion is connected to one of the pair of second power lines; an electric current measurement unit that measures an electric current in the second power lines (17b, 18b); and an arc determination unit that determines whether or not an arc is generated based on a high frequency component of an alternating current measured by the electric current measurement unit, wherein an impedance of the first capacitor satisfies a condition that a combined impedance of the impedance of the first capacitor, impedances of the DC-DC conversion circuit between the pair of first power lines (17a, 18a) and the pair of second power lines (17b, 18b), an impedance of the DC-DC conversion circuit between the pair of second power lines (17b, 18b), and an impedance of the load apparatus is smaller than an impedance of the DC-DC conversion circuit between the pair of first power lines (17a, 18a). a first capacitor whose one end portion is connected to one of the pair of first power lines, and whose other end portion is connected to one of the pair of second power lines; an electric current measurement unit that measures an electric current in the second power lines (17b, 18b); and an arc determination unit that determines whether or not an arc is generated based on a high frequency component of an alternating current measured by the electric current measurement unit, wherein an impedance of the first capacitor satisfies a condition that a combined impedance of the impedance of the first capacitor, impedances of the DC-DC conversion circuit between the pair of first power lines (17a, 18a) and the pair of second power lines (17b, 18b), an impedance of the DC-DC conversion circuit between the pair of second power lines (17b, 18b), and an impedance of the load apparatus is smaller than an impedance of the DC-DC conversion circuit between the pair of first power lines (17a, 18a).