This chapter seeks to clarify the relation between fluid permeability and methane-hydrate saturation (Sh). The ultimate purpose is to estimate the theoretical expression by the equation K = K₀(1 Sh)^N (where K₀ is the apparent permeability at Sh = 0 and N is a constant) for input into methane-hydrate numerical simulators. However, the permeability of hydrate-bearing sediment strongly depends on the hydrate saturation, grain-size distribution, porosity, pore-size distribution, hydrate formation method, and so on. To clarify the relation between the permeability and methane-hydrate saturation, we measured the water permeability of methane-hydrate-bearing sediments with different hydrate saturations for three contrasting methane-hydrate formation methods: (1) the connate water reaction method, (2) the gas diffusion method, and the (3) cementing method. The results demonstrate that the rate of decrease in the apparent water permeability (AWP) with increasing methane-hydrate saturation differs for each method of gas-hydrate formation. In addition, the values of K and N in the theoretical expression K = K₀(1 Sh)^N were estimated for each production method, and a different N value was obtained for each hydrate formation method. It is apparent that the method of gas-hydrate formation leads to a contrasting geometry of methane-hydrate growth at the pore scale and in turn affects the macroscopic AWP saturation relations.