Abstract: To provide an antifouling processing agent composition capable of imparting oil repellency and antifouling properties (stain release properties), while suppressing a reduction in the water absorbency of a textile product. This antifouling processing agent composition comprises: a fluorinated polymer comprising from 30 to 70 mass % of units based on F(CF2)nY—OCOCR?CH2 (wherein Y is an alkylene group, and R is a hydrogen atom, an alkyl group, or a halogen atom) and from 20 to 60 mass % of units based on CH2?CR1—COO—(R2O)q—R3 (wherein R1 is a hydrogen atom or a methyl group, R2 is an alkylene group, and R3 is a hydrogen atom, an alkyl group, a (meth)acryloyl group, or a glycidyl group), and having a number average molecular weight of 3,000-500,000; and a fluorinated amphoteric surfactant having a C1-6 perfluoroalkyl group or a C3-9 perfluoroalkenyl group, and having a number average molecular weight of less than 3,000.