To provide a seat suspension arranged between a vehicular seat and a body of a vehicle for supporting the seat in a vibration-proof manner, achieving lower transmissibility during idling while maintaining damping performance during travelling.

The seat suspension comprises a seat side mounting bracket 12, a body side mounting bracket 14, a rubber elastic body 16 provided between both brackets, a piston member 18 and a cylinder member 20 joined to each other via the elastic body and relatively displaceable in the direction of vibration with the elastic deformation of the elastic body during vibration, a MR fluid 22 having viscosity changed with the strength of a magnetic field, a flow path 24 formed between the piston member 18 and the cylinder member 20 for sealingly holding the MR fluid 22 in a fluidized condition, and an electric magnet 26 for forming a magnetic path crossing the flow path and allowing the control of the strength of the magnetic field to change the viscosity of the MR fluid 22.