Abstract: A method for treating a textile product including, treating the textile product with a treatment liquid and thereafter rinsing the textile product with water, the treatment liquid being obtained by mixing the following components (a) and (b) with water containing a hardness component, provided that the treatment liquid does not include a total of 100 ppm or more of a dicarboxylic acid with 14 or more and 16 or less carbons and a salt thereof, component (a): a sulfosuccinic acid ester having a hydrocarbon group with a predetermined number of carbons or a salt thereof, and component (b): one or more surfactants selected from the following components (b1) and (b2), component (b1): an anionic surfactant (excluding component (a)), and component (b2): a predetermined nonionic surfactant, wherein the treatment liquid satisfies any of the following requirements (1) and (2), requirement (1): content proportion (a)/[(a)+(b1)] is more than 0 mass % and 50 mass % or less, and requirement (2): content proportion (a)/[(