A cleaning composition which is capable of removing both organic soiling and particulate soiling adhered to a substrate for an electronic device with a high degree of cleanliness, and which also has minimal impact on the environment, as well as a method of cleaning a substrate for an electronic device. The present invention relates to a cleaning composition used for cleaning a substrate for an electronic device including a water-soluble salt (A) containing a transition metal, a chelating agent (B) and a peroxide (C), wherein the amount of the chelating agent (B) is not less than 0.5 molar equivalents relative to the amount of the water-soluble salt (A) containing a transition metal.