A harmonic detection system (1) comprises a measurement component (71), a harmonic abnormality determination unit (561), and a smartphone (9). The measurement component (71) is installed at a specific position on a distribution line constituting a distribution network (100), and measures data related to the current of the distribution line. The harmonic abnormality determination unit (561) uses some or all of the data related to current as detection data to detect abnormality related to harmonics. The smartphone (9) is owned by a user (G), and notifies the user that an abnormality has occurred in the distribution line when a harmonic is detected.