The present invention provides a copolymer whose durability on cleaning is improved while maintaining good water- and oil-repellency. Disclosed is a copolymer having: (i) a fluoroalkyl group, (ii) a urethane or urea linkage, and (iii) a functional group selected from the group consisting of a carboxyl group, a carboxylic anhydride group, an epoxy group, a phosphoric group, an alkoxysilane group, a imine group, a sulfonic group, an amino group, an isocyanate group and a chlorine atom, and a stainproof agent containing the copolymer as an active component.