To heighten the generation efficiency of a hydrogen gas inclusion hydrate and to make the device for manufacturing the hydrogen gas inclusion hydrate compact.

An upper part space 5, a trunk part space 6, and a lower part space 7, which are partitioned by an upper part pipe plate 3 and a lower part pipe plate 4, are formed in a pressure vessel 2. A generation vessel 1 is formed in such a way that the upper part space 5 and the lower space 7 are communicated to each other through a number of vertical cooling pipes 8 penetrating the trunk part space 6. A hydrogen gas supplying line 9 and an unreacted water recycling line 11 are connected to the upper part space 5. A cooling medium supplying part is connected to the trunk part space 6 via a supplying line 15 and a returning line 16 which supply and return a cooling medium 17 respectively. By bringing water 12 in contact with a hydrogen gas 10 pressurized to about 200 MPa and supplied while cooling the water 12, which is allowed to flow down in a state of a water film along the inside surface of the cooling pipe 8, to about -25°C with the cooling medium 17 in the trunk space 6, a hydrogen gas inclusion hydrate 14 is generated. An unreacted hydrogen gas 10, which is mixed in the hydrogen gas inclusion hydrate 14 and taken out from the lower space 7, and the water 12 are recycled as raw materials after separated in a generated product separation vessel 18.