An arc detection circuit that detects an arc that occurs in a transmission path that transmits power from a power supply apparatus to a power conditioner, the arc detection circuit includes: a current detector that detects a current flowing through the transmission path; a storage unit configured to store a base characteristic which is a frequency characteristic of the current flowing through the transmission path when the arc is not present; and an arc determination unit configured to determine whether the arc has occurred based on a result of a comparison between the base characteristic and a detection characteristic which is a frequency characteristic of the current detected by the current detector.