There is provided a process for producing a DDR-type zeolite having: a raw material solution preparation step of preparing a raw material solution containing 1-adamantaneamine hydrochloride, silica (SiO2), and water at a 1-adamantaneamine hydrochloride/SiO2 molar ratio of 0.002 to 0.5 and a water/SiO2 molar ratio of 10 to 500, and a crystal growth step of subjecting the raw material solution and a DDR-type zeolite powder to a heat treatment in a state that both the raw material solution and the DDR-type zeolite powder are brought into contact with each other to grow crystals of the DDR-type zeolite by the use of the DDR-type zeolite powder as seed crystals.