A viscous damper wherein the viscosity of a fluid, such as an oil, is used to generate damping effect when the fluid is passed through a restricted orifice or slit. Electrodes are arranged to face each other across the orifice or slit so that an electric field is created in a direction which is transverse to the direction of the fluid flow in the orifice or slit. The voltage applied to the electrodes is controlled in accordance with a frequency of vibration of a vibrating member to be damped. The viscosity of the fluid is controlled by applying a voltage thereto, so that a desired damping effect is obtained within a wide range of the frequency of the vibrating body.