It is an object of the present invention to provide a polymer material, the histocompatibility of which has been improved by irradiation of ion beam, which prevents an aneurysm having a risk of rupture from actually rupturing. The present invention provides a material for treating aneurysms, which is composed of a polymer material containing carbon as a constitutional element, and which is produced by modifying at least a portion of the surface thereof by ion bombardment.
