PURPOSE: To decrease the number of parts, so as to shorten a seal mechanism part by providing a rotary ring fixed perpendicular to a rotary shaft, providing a fixed ring in contact with one rotational side surface of the rotary ring, and arranging a fluid side seal surface and an atmospheric side seal surface on this surface while pinching a pressurized pocket between those seal surfaces located outside and inside thereof in the radial direction.

CONSTITUTION: A rotary ring 2 is fixed perpendicular to a rotary shaft by a shaft sleeve 11 through an O-ring 10. A fixed ring 3 is attached to a presser plate 9 so as to be faced to the rotary ring 2 in the state where it can be axially moved. A fluid side seal surface 12 for gas or liquid and an atmospheric side seal surface 13 are provided on the surface of the fixed ring 3, to be brought in contact with the rotary ring 2 while pinching a pressurized pocket 14 composed of a groove between both sides and one rotational side surface 2a of the rotary ring 2. Thereby, two rotary rings axially arranged in the past can be decreased into a single ring, thereby the axial length can be shortened, and the number of parts can be decreased.