An indicator for a connector, which is attached to a connector, has a first indication member at which is indicated first information urging a user to perform a predetermined operation before using the connector, and which is attached to a position such that the connector cannot be connected if the user does not remove the indicator for a connector, and which can be removed from the connector. The indicator for a connector also has a second indication member at which is indicated second information which is useful at a time of connecting the connector, the second indication member being attached to a position which does not impede connection of the connector.