Cationic electrodeposition coating composition

A cationic electrodeposition coating composition comprising an aminated epoxy resin and a blocked polyisocyanate curing agent, wherein

• the aminated epoxy resin is an aminated epoxy resin obtained by reacting an amine compound with an epoxy resin,
• the amine compound is a combination of a first amine and a second amine,
• the first amine is represented by a formula:
• NH2—(CH2)n-NR1R2 (1)
• in the formula (1), R1 and R2 are the same or different and each represent an alkyl group having 1 to 6 carbon atoms and optionally having a hydroxy group at a terminal thereof, and n represents an integer of 2 to 4, and
• the second amine is represented by a formula:
• R3R4NH (2)
• in the formula (2), R3 and R4 each represent an alkyl group having 1 to 4 carbon atoms and having a hydroxy group at a terminal thereof,
• a tertiary amination rate of the amine compound in obtaining the aminated epoxy resin, which is calculated by tertiary amine value/total amine value×100, is 85% or more,
• the epoxy resin is a polyphenol polyglycidyl ether type epoxy resin,
• the aminated epoxy resin has a molecular weight distribution of 2.7 or less, and
• a rate of elongation of an electrodeposition coating film formed by applying the cationic electrodeposition coating composition to a steel sheet such that a cured film thickness is 20 μm, followed by baking at 160° C. for 15 minutes, is 0.1 to 4.5%.