A sealing device, comprising: a movable part which is fixed to a shaft penetrating a wall of a vessel and is movable with the shaft, the vessel being configured to include an interior space having a higher pressure or a lower pressure than an exterior space; a first bellows part which has a first end fixed to the vessel and a second end fixed to the movable part, for sealing a penetrated portion of the vessel by the shaft; a second bellows part which is disposed opposite to the first bellows part across the movable part, and has a first end disposed on a side of the first bellows part and fixed to the movable part, and a second end fixed to a stationary member; and a communication path for causing an interior space of the first bellows part and an interior space of the second bellows part to communicate with each other; characterized in that the shaft includes: a first shaft part penetrating the wall of the vessel and connected to the movable part; and a second shaft part disposed opposite to the first shaft part across the movable part, in that the sealing device is configured such that a driving force in an axial direction is applied to one of the first shaft part or the second shaft part, and in that the sealing device is configured such that the driving force from the one of the first shaft part or the second shaft part is transmitted via the movable part to the other of the first shaft part or the second shaft part, in that the sealing device comprises a link which extends beyond the second bellows part in the axial direction is connected at one end to the movable part, and is connected at another end to the second shaft part, and in that the sealing device is configured such that the driving force applied to the one of the first shaft part or the second shaft part is transmitted via the link to the other of the first shaft part or the second shaft part. a movable part which is fixed to a shaft penetrating a wall of a vessel and is movable with the shaft, the vessel being configured to include an interior space having a higher pressure or a lower pressure than an exterior space; a first bellows part which has a first end fixed to the vessel and a second end fixed to the movable part, for sealing a penetrated portion of the vessel by the shaft; a second bellows part which is disposed opposite to the first bellows part across the movable part, and has a first end disposed on a side of the first bellows part and fixed to the movable part, and a second end fixed to a stationary member; and a communication path for causing an interior space of the first bellows part and an interior space of the second bellows part to communicate with each other; characterized in that the shaft includes: a first shaft part penetrating the wall of the vessel and connected to the movable part; and a second shaft part disposed opposite to the first shaft part across the movable part, a first shaft part penetrating the wall of the vessel and connected to the movable part; and a second shaft part disposed opposite to the first shaft part across the movable part, in that the sealing device is configured such that a driving force in an axial direction is applied to one of the first shaft part or the second shaft part, and in that the sealing device is configured such that the driving force from the one of the first shaft part or the second shaft part is transmitted via the movable part to the other of the first shaft part or the second shaft part, in that the sealing device comprises a link which extends beyond the second bellows part in the axial direction is connected at one end to the movable part, and is connected at another end to the second shaft part, and in that the sealing device is configured such that the driving force applied to the one of the first shaft part or the second shaft part is transmitted via the link to the other of the first shaft part or the second shaft part.