An input energy saving device for a low frequency vibration type washing machine. The device lets the resonance frequency of the washing tub and the input frequency of the oscillating disc be equal to each other during generation of resonance phenomena in the multi-phase washing medium for clothes washing, thus to save the input energy required in generation of the resonance phenomena. The device comprises a washing tub receiving multi-phase washing medium therein and an oscillating disc provided in the washing tub for generation of resonance phenomena in the washing medium. A flexible elastic body is placed between the disc and the inner bottom of the washing tub for letting the input frequency of the disc means and the resonance frequency of the washing tub be equal to each other. An actuator is coupled to the disc through a shaft so as to drive the disc means.