To provide a transmission for providing the infinite variable ratio not the limited number of different driving ratios.

This transmission is provided with a series of discs 12 and plates 14 provided in a chamber 20, the discs 12 are connected to a first shaft 16, the plates 14 are connected to a second shaft 18, and magnetorheological fluid(MR fluid) exists between the discs 12 and the plates 14. One or more electric coils 24, 26 are arranged in the chamber, and the magnetorheological fluid is exposed to the magnetic filed, to make changeable by an electronic controller. When voltage and current are applied to the electric coils 24, the magnetic field generated by one or more electric coils 24 changes viscosity of magnetodynamic fluid to change the slip ratio between the discs 12 and the plates 14.