A self-crosslinkable resin prepared by (1) reacting a hydroxy-containing vinyl monomer with some isocyanate groups on the skeleton of a vinyl polymer having at least two isocyanate groups in the molecule to introduce a polymerizable double bond into the polymer, subsequently completely blocking the isocyanate group(s) remaining on the polymer skeleton with a blocking agent, and thereafter polymerizing an unsaturated monomer component consisting essentially of a hydroxyl-containing vinyl monomer with the polymerizable double bond introduced; or (2) blocking some isocyanate groups on the polymer skeleton with a blocking agent, subsequently reacting a hydroxyl-containing vinyl monomer with the isocyanate group(s) remaining on the polymer skeleton to introduce a polymerizable double bond into the polymer, and thereafter polymerizing an unsaturated monomer component consisting essentially of a hydroxyl-containing vinyl monomer with the polymerizable double bond introduced.