<p>A swellable oil-absorbent agent formed of a cross-linked polymer (P) obtained by polymerizing a monomer component comprising 90 to 99.999% by weight of a monomer having as a main moiety thereof an alkyl (meth)acrylate the alkyl group of which has 10 to 16 carbon atoms and possessing one polymerizable unsaturated group in the molecular unit thereof and 0.001 to 10% by weight of a cross-linkable monomer possessing at least two polymerizable unsaturated groups in the molecular unit thereof (providing that the total of the amount of the polymerizable monomer and that of the cross-linkable monomer is 100% by weight).</p>
