PURPOSE: To obtain a shaft sealing apparatus having high reliability for shaft sealing by providing a small gap between the external circumference of poles and a housing to form a magnetic field which is equilibrium to the internal circumferential portion in view of sealing a shaft by leaving a magnetic fluid.

CONSTITUTION: A magnetic fluid 7 is left, with formation of magnetic field due to an electromagnet 6, at a small gap δ provided between the internal circumference of poles 9, 10 and a rotating shaft 1 and the poles 9, 10 are formed to provide a small gap against a housing 11 by applying such magnetic fluid to a shaft sealing mechanism which is supported by a rubber ring 8 provided against the internal circumferential surface of the housing 11 supported through a bearing 4. Simultaneously, a magnetic field which is equilibrium to the internal circumferential portion of the poles 9, 10 is formed against a weak magnetic material housing 11 to leave the magnetic fluid 7 in view of sealing the shaft with the internal and external circumferences of the poles 9, 10. Thereby, highly reliable shaft sealing apparatus can be obtained by sealing the shaft with magnetic fluid which can alleviate vacuum transmissivity of the rubber ring.