To provide a barrier agent composition against lubricating oils that has both safety for living organisms and the environment and performances equal or superior to those of conventional barrier agent compositions comprising a compound bearing an 8C or higher polyfluoroalkyl group and exhibits an excellent drying property.

The barrier agent composition against lubricating oils comprises a polymer (1) that comprises at least 90 mass% of a polymerized unit (A) derived from a compound represented by formula (a): CH2=C(R1)-CO-Q1-Rf (a) and at most 10 mass% of a polymerized unit (B) derived from a hydroxy group-bearing unsaturated compound and a fluorine-containing solvent (2) and has a weight-average molecular weight of at least 500,000. In the formula (a), Q1 is a single bond or a bivalent linking group; R1 is a hydrogen atom or a methyl group; and Rf is a 1-6C polyfluoroalkyl or polyfluoroether group.