A washing machine including a tub to retain wash water, a spin basket rotatably installed in the tub, a pulsator rotatably installed in the spin basket, a drive unit to generate rotary power and transmit the rotary power to the pulsator, and a float clutch elevatably installed at the pulsator to selectively transmit the rotary power to the spin basket when elevated by buoyancy. The float clutch includes guide protrusions provided at an upper surface thereof to allow the float clutch to be elevatably installed at a lower portion of the pulsator, and the pulsator includes guide grooved provided at a lower surface thereof, the guide protrusions being elevatably installed in the guide grooves. Since the float clutch receives rotary power at a position spaced apart from the shaft installation portion of the pulsator, the rotary power is prevented from being concentrated on the shaft installation portion.