It is an object of the present invention to provide a cationic electrodeposition coating composition which is free of toxic rust-preventive pigments such as lead compounds and capable of giving coating films having high resistance to corrosion and rusting, even when applied to a substrate surface which is only insufficiently subjected, to a chemical conversion treatment. The present invention provides a cationic electrodeposition coating composition which comprises a rust inhibitor comprising at least one compound selected from the group consisting of compounds containing any of elemental metals belonging to the period 4, 5 or 6 of group 3 of the periodic table and a sulfonium- and propargyl group-containing resin composition. For, example, the content of said rust inhibitor is 0.03 to 10 weight parts in terms of the elemental metal in the rust inhibitor based on 100 weight parts of the solid resins in the resin composition.