The present invention aims at dissolving hydrogen gas in a liquid and maintaining the solubility of the hydrogen gas in the liquid at a high state.A sealing bag 1 that dissolves hydrogen gas in a liquid by being put into the liquid includes a hydrogen permeable film that can permeate hydrogen gas that is sealed and filled in the sealing bag to outside. By sinking this sealing bag 1 into the liquid in advance, the hydrogen gas that is permeated through the hydrogen permeable film is dissolved in the liquid. Furthermore, since the hydrogen gas is continuously permeated little by little through the hydrogen permeable film, the solubility of the hydrogen in the liquid can be maintained at a high state.