The invention has an object to provide a copolymer, which enables to yield a coated film with a high transparency when formed into a coated film, and to add a regenerable antibacterial effect, as well as a resin composition containing the same. A copolymer of the invention is a copolymer including a repeating unit represented by the following formula (I) (wherein R 1 represents a hydrogen atom or a methyl group； R 2 represents a hydrogen atom or a saturated or unsaturated alkyl group having 1 to 18 carbon atoms； R 11 to R 14 each independently represent a hydrogen atom or an alkyl group, provided that at least 2 of R 11 to R 14 represent an alkyl group, and that R 11 and R 12 , or R 13 and R 14 can bond together to form a ring； X represents -O- or -NR 20 -； R 20 represents a hydrogen atom or an alkyl group； Y represents a halogen atom； and n represents 0 or 1), and a repeating unit having a crosslinkable functional group.本發明之課題在於提供一種於製成塗膜時可獲得高透明性之塗膜且可賦予可再生之抗菌效果之共聚物、及含有其之樹脂組合物。本發明之共聚物係包含下述式(I)所表示之重複單元及具有交聯性官能基之重複單元之共聚物。(式中，R1表示氫原子或甲基，R2表示氫原子、或碳數1~18之飽和或不飽和烷基，R11~R14分別獨立地表示氫原子或烷基，其中，R11~R14中之至少2者表示烷基，R11與R12、或R13與R14亦可鍵結而形成環，X表示-O-或-NR20-，R20表示氫原子或烷基，Y表示鹵素原子，n表示0或1)。
