A vinyl acetylsalicylate-vinyl alcohol based copolymer which comprises a structural unit having the following formula (1): <CHEM> and a structural unit having the following formula (2): <CHEM> optionally with at least one member selected from the group consisting of a structural unit having the following formula (3): <CHEM> and a structural unit having the following formula (4): <CHEM> In the copolymer, the amounts of vinyl acetylsalicylate units and vinyl alcohol units, degree of polymerization and the like can be controlled, whereby the efficacy of acetylsalicylic acid can be easily controlled as desired. Therefore, the copolymer is expected to be widely applicable as medicament.
