[Problem] To provide a composition for forming a coating film that effectively inhibits the adhesion of cells such as platelets and a biomaterial such as a protein. [Solution] The invention provides an adhesion inhibitor, for cells and a biomaterial, comprising a polymer having a structural unit represented by formula (1), a crosslinking material, and an organic solvent. In formula (1), R1 represents a C4-20 organic group containing one or two aromatic or alicyclic hydrocarbons, each n represents an integer from 5 to 600, and Q represents either formula (2), (3), (4), or (5) (in formula (2), Q1 represents a dihydric organic group, and each m independently represents either 0 or 1, and in formulas (3), (4), and (5), R2, R3, R4, and R5 each independently represents a hydrogen atom or an organic group).本發明之課題係提供一種為形成對蛋白質等生體物質,或血小板等細胞具有附著抑制效果之被覆膜之組成物。解決方法係提供一種生體物質或細胞之附著抑制劑,其係含有具有以下述式(1)表示之構造單位之聚合物、交聯劑以及有機溶媒,其中,下述式(1):[式中,R1係表示含有1個或2個芳香族烴或脂環式烴之碳數為4至20的有機基,2個n係分別表示5至600的整數,Q係以下述式(2)、式(3)、式(4)或式(5)表示之二價的有機基:(式中,Q1係表示二價的有機基,2個m係分別表示獨立的0或1,)(式中,R2、R3、R4以及R5係分別表示獨立的氫原子或有機基)]。
