SEALING DEVICE

PROBLEM TO BE SOLVED: To provide a sealing device capable of using even a stretching body slight in a fluctuation of a pressure in the stretching body and low in pressure resistance. SOLUTION: A reciprocating body 6 extending from the outside through the inside of a fluid chamber 1 is reciprocated and outside air is prevented from penetrating in the fluid chamber through an engagement part between the fluid chamber and the reciprocating body. In the so formed sealing device, a first stretching body 9 is mounted between a fluid chamber wall having an engaging part and the surface of a moving plate 7 mounted on the reciprocating body and such that penetration of external fluid into a gap between the fluid chamber wall and the moving plate is cut off by surrounding the first stretching body 9. A second stretching body 9a is mounted between the moving plate and a fixed plate 11 such that penetration of external fluid to a gap between the moving plate and the fixed plate 11 is cut off. Fluid at the inside of two stretching bodies is capable of flowing through a communication hole 7a formed in the inside of the moving plate.