The purpose of the present invention is to provide a polymer film which can conform to movements of the living body or to fine ruggedness and further has excellent adhesion to biotissues. The present invention provides a polymer film which has a thickness of 10 1 000 nm and comprises a block copolymer having a structure in which a branched poly(alkylene glycol) and a poly(hydroxyalkanoic acid) have been bonded to each other. The branched poly(alkylene glycol) has three or more terminal hydroxyl groups per molecule. The proportion of the mass of the branched poly(alkylene glycol) to the whole mass of the block copolymer is 1 30%. When the average molecular weight of the poly(hydroxyalkanoic acid) contained in the block copolymer is divided by the number X of the terminal hydroxyl groups possessed by the branched poly(alkylene glycol) per molecule then the quotient is 10 000 30 000.
