The object of the present disclosure is to provide a crosslinked resin fine particle which has a particle diameter small enough to be used suitably for the purpose of viscosity control and can be produced inexpensively. Crosslinked resin fine particles obtained by reacting a vinyl monomer composition comprising: 5 to 50% by weight of a (meth)acrylamide-based monomer (A), 5 to 50% by weight of a crosslinkable unsaturated monomer (B), and 10 to 90% by weight of a (meth)acrylate having an alkyl group containing 8 to 24 carbon atoms (C) in an organic solvent, and having a number average particle diameter of 10 to 250 nm.