The detoxification method characterized by comprising converting at least one member selected from the group comprising arsenic, antimony and selenium into a harmless substance produced in a food chain system by using the food chain system. The method of detoxifying a harmful compound as described above is characterized by comprising converting a harmful compound containing at least one element selected from the group comprising arsenic, antimony, and selenium into a harmless substance by using a food chain system containing a larval zooplankton.