Resin composition for sealing

Provided are a resin composition for sealing, having the combination of good transparency, moisture permeation resistance, and adhesive wet-heat resistance, and a resin composition for sealing that is obtained from the resin composition. A resin composition containing (A) a styrene-isobutylene modified resin and (B) a tackifying resin is used to obtain a resin composition for sealing, and a resin composition layer of the resin composition on a support is formed to obtain a sheet of the resin composition for sealing.