To provide a slipperiness-imparting agent capable of imparting durable slipperiness (in particular, slipperiness when wet). The present invention was completed upon the discovery that a slipperiness-imparting agent can impart durable slipperiness to a base material surface by using a simple method called light irradiation, said slipperiness-imparting agent containing: a copolymer containing a structural unit (A) based on 2-methacryloyloxyethyl phosphorylcholine and a structural unit (B) based on a photoreactive functional group-containing monomer； or a copolymer containing a structural unit based on a structural unit (A) based on 2-methacryloyloxyethyl phosphorylcholine, a photoreactive functional group-containing monomer (B), and a hydrophobic group-containing monomer (C).本發明提供一種滑性賦予劑，其能夠賦予基材具有耐久性的滑性（特別是濕潤時滑性）。本發明的發明人們發現，含有共聚物的滑性賦予劑能夠藉由光照射這種簡單方法，賦予基材表面具有耐久性的滑性，從而完成了本發明。所述共聚物，含有基於2-甲基丙烯醯氧基乙基磷酸膽鹼的結構單元（A）與基於含光反應性官能團單體的結構單元（B）；或含有基於2-甲基丙烯醯氧基乙基磷酸膽鹼的結構單元（A）、基於含光反應性官能團單體的結構單元（B）、以及基於含疏水性基團單體的結構單元（C）的聚合物的滑性賦予劑。
