A polymer including a structural unit as shown in formula (1) is useful for enhancing the adhesiveness of cancer cells on the surface of a filter and the concentration rate of cancer cells by being applied on the surface of a cancer cell concentration filter. In the formula (1), R1 is a hydrogen atom or a methyl, R2 is a methyl or an ethyl, and m is 1-3.含有下述通式(1)所表示的結構單元的聚合物藉由應用於癌細胞濃縮過濾器的表面,可提高癌細胞對過濾器表面的貼附性,提高癌細胞的濃縮率,因此有用。式中,R1為氫原子或甲基,R2為甲基或乙基,m為1~3。