A malfunction diagnosis system includes: a malfunction diagnosis section that performs a malfunction diagnosis for an on-board device of an electric vehicle when supplied with electric power from either an electric storage section or an external power source; a malfunction diagnosis request section that requests the malfunction diagnosis section to carry out malfunction diagnosis; an external power source connector that supplies electric power from the external power source; and an external power source connection determination section that determines whether the external power source connector is connected to the external power source. The malfunction diagnosis request section changes at least either the number of times that the malfunction diagnosis section is requested to carry out malfunction diagnosis or the period of time the malfunction diagnosis section is requested to carry out malfunction diagnosis depending whether the external power source connector is connected to the external power source.