PROBLEM TO BE SOLVED: To provide a gas seal device for reducing labor when replenishing liquid, by not only preventing leakage of the liquid but also labor for automatical supply of sealing liquid. SOLUTION: A storage pot 26 is arranged in a part of a rotary shaft 20 near an upper wall surface 14A in a digestive tank 14. While having a clearance with a bottom surface 26A of the storage pot 26 on the inner surface side of a through-hole 18, an intermediate cylinder 28 formed in a smaller diameter than the storage pot 26 is fixed, and the liquid L is stored inside these. A buffer tank 30 storing the liquid L is arranged outside the digestive tank 14, and the other end side of an upper pipe 32 having one end connected to the intermediate cylinder 28 extends to the buffer tank 30, and the other end of the upper pipe 32 is arranged on a liquid level of the liquid L stored in the buffer tank 30. The other end of a lower pipe 34 having one end connected to a lower side part of the upper pipe 32 of the intermediate cylinder 28, is connected to a lower end part of the buffer tank 30. COPYRIGHT: (C)2010,JPO&INPIT