To prevent leakage of a fluid from the circumference of a rotary shaft of a rotor.

In this rotary shaft seal system, an elastic ring has an internal diameter smaller than a rotary shaft diameter, applied with a taper, and has an external diameter in time of installation larger than a diameter of an opening part 5 of a housing so as to prevent the leakage of the fluid from the circumference of the rotary shaft 2 related to the rotary shaft seal system. By applying a slit 4 to the elastic ring, displacement of a position is prevented. By making the the elastic ring corotate simultaneously with rotation of the rotary shaft by pressing the elastic ring into the opening part, an elastic body 1 is compressed, and repulsion thereof seals the fluid.