The present invention provides an adhesive composition for optical use, which includes rubber and may be chemically cross-linked through an appropriate curing process, and as a result, may secure excellent long-term durability, water vapor transmission resistance, and chemical resistance, and includes an isobutylene-isoprene rubber having an acrylic acid ester-based functional group in a main chain thereof, a photoinitiator, and a tackifier in order to provide optical characteristics sufficient to be used for optical use. The present invention provides a method for preparing the adhesive composition for optical use, and it is possible to obtain the adhesive composition for optical use, which includes a chemically cross-linkable rubber by the method. Further, the present invention provides an adhesive film for optical use, and excellent long-term durability and optical characteristics may be implemented by applying the adhesive film for optical use to a wide range of electronic devices.