According to the present invention, a sealing material for a high-pressure hydrogen container, which mainly comprises a silicone rubber composed of a dimethyl siloxane segment, a methyl vinyl siloxane segment, and a diphenyl siloxane segment, and a high-pressure hydrogen container using the sealing material are provided. In order to seal a high-pressure hydrogen container (CHG tank) system for fuel cell vehicles with an elastomer, the elastomer has (1): excellent durability in a variable pressure environment of high-pressure hydrogen; and (2): excellent sag resistance in low-temperature to high-temperature environments, and thus the significant technical objectives (1) and (2) have been achieved.