A washing machine having a sub-pulsator, the washing machine including a pulsator rotating in the left/right directions by a driving source during the washing process and guide duct mounted in a wash/spin-dry tub for guiding the washing water agitated by left/right rotations of the pulsator to the upper side of the wash/spin-dry tub, wherein the washing machine comprises:a hydraulic turbine disposed in the guide duct; anda sub-pulsator arranged in the wash/spin-dry tub to mesh with the hydraulic turbine, such that a side water current is formed at an intermediate section of the wash/spin-dry tub without recourse to input of separately added power to thereby improve the washing performance.