The composition of raw mixed gas and the gas composition of produced mixed gas hydrate are uniformed as rapidly as possible. The process for producing a mixed gas hydrate comprises the gas hydrate forming step of reacting a mixed gas (g) with water (w) to thereby obtain a gas hydrate in slurry form; the dewatering step of removing the water (w) from the gas hydrate slurry (s); the palletizing step of forming the gas hydrate after water removal into pellets; the freezing step of chilling the gas hydrate pellets (p) to the freezing point or below to thereby freeze the same; and the pressure reduction step of depressurizing the frozen gas hydrate to storage pressure, wherein the mixed gas (g) fed to the gas hydrate forming step is diluted by diluent gas (m) as a constituent of the principal components of the mixed gas (g).