An arc detection device is used in a system including one or more power sources, a plurality of converters, and a plurality of load devices. The one or more power sources and the plurality of converters are connected to each other by a plurality of power lines. The plurality of converters and the plurality of load devices are connected to each other by a plurality of power lines. The arc detection device includes: an electric current detector that includes a magnetic core through which two or more power lines included in the plurality of power lines extend, and detects combined currents flowing through the two or more power lines according to the magnetic field produced at the magnetic core; and an arc determiner that determines, on the basis of the combined currents detected by the electric current detector, whether an electric arc has occurred.