With the development of methane hydrate energy resources and new projects such as geological storage of carbon dioxide using hydrates (CO2 hydrate storage), research on the mechanical properties of gas hydrate-bearing ground has been promoted. In this study, we focused on the difference in mechanical properties due to the morphology of hydrate in the void of soil, and attempted to reproduce the various mechanical tests of hydrate-bearing soils using the elastoviscoplastic constitutive equation. In addition, by comparing the material parameters determined by fitting, the relationship between the hydrate formation process and mechanical properties was discussed.