An adhesive encapsulating composition and an encapsulating film, which are useful as an encapsulant for an organic electroluminescence device or other electronic devices is provided. The adhesive encapsulating composition includes a hydrogenated cyclic olefin-based polymer and a polyisobutylene resin having a weight average molecular weight of 500,000 or more. Some embodiments of the adhesive encapsulating.cndot.composition include a hydrogenated cyclic olefin-based polymer, a polyisobutylene resin having a weight average molecular weight of 500,000 or more, a photocurable resin, and a photopolymerization initiator.