A fluorine-containing polymer including: (a) a repeat unit in which the α-position is an acrylate ester monomer substituted with a monovalent organic group or a halogen atom and which is derived from a fluorine-containing monomer having a fluoroalkyl group; (b) a repeat unit which is an alkyl acrylate having a C6-13 alkyl group and is derived from a non-fluorine monomer; and (c) a repeat unit derived from a non-fluorine (meth)acrylate monomer having a cyclic hydrocarbon group. Also disclosed is a surface treatment agent containing the fluorine-containing polymer, a method of treating a substrate with the surface treatment agent and a treated substrate.