To provide a stain-proofing agent having excellent oil-repelling property and oily stain-removing property and having durability to washing without particularly inhibiting water absorbing property to natural fibers, especially cotton.

This comprises 0.1-50 wt.% (based on solid content) aqueous dispersion of a reaction product obtained by copolymerizing a perfluoroalkyl phosphate compound represented by general formula 1: [Rf1-A-O]m-P(O)(OH)n(O-)3-m-n-(Y1+)3-m-n [wherein Rf1 is a 6-20C perfluoroalkyl group; A is a 1-6C alkylene group; m is an integer of 1-2; n is an integer of 0 or 1 and m+n≤2; Y1+ is a pair ion; P is phosphorus atom and the phosphorus content in the compound is 2.2-7.0 wt.%] with a (meth)acrylate containing sulfo group represented by general formula 2: CH2=C-(R2)-(D)i-(E)k-SO3--Y2+ [wherein D is ethylene group or an amide group; E is a 1-6C alkylene group; R2 is hydrogen atom or methyl group; i is an integer of 0 or 1; k is an integer of 0 or 1; Y2+ is a pair ion] and a (meth)acrylate containing a polyalkylene glycol group represented by general formula 3: CH2=C(R3)-(O-R4) I-(O-R5)o-O-R6 [wherein R3 is hydrogen atom or methyl group; R4 is a 1-6C alkylene group; R5 is 1-6C alkylene group; R6 is hydrogen atom or methyl group, ethyl group, phenyl group or a phenyl-substituted 1-6C alkyl group; I is an integer of 1-100 and o is an integer of ≥0 and 1+o≤100] in 1.0-2.5 weight ratio of the compounds of formulas 2 and 3 to the compound (as a solid content) of formula I in an aqueous dispersion of the phosphate compound of formula 1. A polymerization ratio (wt.%) of the acrylate represented by general formula 2 to the acrylate represented by general formula 3 is (30-70)/(70-30).