Abstract: The present invention is a friction reducing agent for fibers containing the following components (a) and (b), and further, a detergent composition for fibers containing the following components (a) and (b), wherein a proportion of a content of component (b) to a total content of components (a) and (b) is 20 mass % or more and less than 100 mass %, component (a): an internal olefin sulfonate with 17 or more and 24 or less carbons, and component (b): a sulfosuccinic acid ester or a salt thereof having a hydrocarbon group with 5 or more and 18 or less carbons.

Abstract: The present invention is a detergent composition for fibers that contains components (a) and (b) described below and satisfies at least one requirement of the following: requirement (1) a proportion of a content of component (a) to a total content of components (a) and (b1) is 35 mass % or more and 80 mass % or less; and requirement (2) a proportion of the content of component (a) to a total content of components (a) and (b2) is 50 mass % or more and 80 mass % or less. Component (a) is a sulfosuccinic acid ester or a salt thereof having a branched hydrocarbon group with 5 or more and 18 or less carbons, and component (b) is one or more surfactants selected from the following components (b1) and (b2): component (b1) an anionic surfactant (excluding component (a)); and component (b2) one or more nonionic surfactants selected from an aliphatic alcohol alkoxylate and an ester alkoxylate.