To provide a stain-proofing coating agent which shows excellent cohesiveness on a plasticizer-containing plastic film, excellent stain-proofness, easy removal of dirt and almost no stain of dirt.

This stain-proofing coating agent comprises a polymer (A) comprising (a) 5-70 wt.% of (meth)acrylonitrile, (b) 5-40 wt.% of a monomer having a carbon-carbon unsaturated double bond and a crosslinkable functional group, and (c) 90-0 wt.% of a monomer copolymerizable with (a) or (b) and a polymer (B) comprising (d) 5-60 wt.% of a carbon-carbon unsaturated double bond and a polyorganosiloxane chain, (b) 5-40 wt.% of a monomer having a carbon-carbon unsaturated double bond and a crosslinkable functional group and (c) 90-0 wt.% of a monomer copolymerizable with (a) or (b).