This invention discloses a cationic electrodeposition paint composition containing an amino group-containing modified epoxy resin which is obtained through reaction of specific modified epoxy resin with xylene formaldehyde resin having phenolic hydroxyl groups and amino group-containing compound. The cationic electrodeposition paint composition excels in film thickness retention, finished appearance of coating film and electrocoatability of galvanized alloy steel sheet and can form coating film having good corrosion resistance, even when its content of volatile organic compound (VOC) is reduced.