PURPOSE: To keep off any leakage of a fluid from a vane side surface as well as to improve efficiency in a vane compressor, by forming an inner surface of a side cover with a magnet, while sealing a magnetic fluid in space between the inner surface of this side cover and each side of a vane and a rotor and holding it.

CONSTITUTION: In an inner surface of a side cover 2, there is provided with the side cover groove part 8 formed in accord with the form of rotational space of a cylinder 1, and a ring magnet 9 is embedded in this side cover groove part 8. In addition, a magnetic fluid 10 is sealed in space between the inner surface of this side cover 2 and each side of a vane 5 and a rotor 4, and it is held by dint of magnetic force of the magnet 9. With this constitution, since an interval between the inner surface of the side cover 2 and each side of the vane 5 and the rotor 4 is hermetically sealed by the magnetic fluid 10, any leakage of the fluid from a side face of the vane 5 is prevented from occurring, thus any drop in efficiency of a vane compressor is kept back.