Biological material adhesion inhibitor

A composition for forming a coating film having the ability to inhibit adhesion of biological substances, the composition comprising a copolymer and a solvent, wherein the copolymer is obtained by subjecting a monomer mixture to polymerization, the monomer mixture comprising

• a compound represented by the following formula (1-3):
• wherein and n represents an integer of 3 to 6,
• a compound represented by the following formula (2):
• wherein R3 represents a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms, and R4 represents a cationic monovalent organic group, and
• a compound represented by the following formula (3):
• wherein each R5 independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, R6 represents a linear or branched alkylene group having 1 to 10 carbon atoms which may be substituted with a halogen atom, and m represents an integer of 1 to 30,
• wherein the amount of the compound represented by the formula (3) is 2 to 40% by mass, based on the mass of the monomer mixture.