Disclosed is a water supply apparatus for washing machines having a simplified structure. The water supply apparatus is usable in a washing machine, which has a drum to accommodate laundry, and a detergent supply apparatus including a dispenser provided with a plurality of channels to supply water to a plurality of detergents to be supplied to the drum, and includes at least one water supply pipe extending from the rear portion of the washing machine to the detergent supply apparatus to supply water to the dispenser, a nozzle provided with one end connected to the at least one water supply pipe and the other end disposed adjacent to entrances of the plurality of channels, and being rotatable to supply water selectively to one of the plurality of channels, a drive unit generating drive force to rotate the nozzle, and a rotation control device to control rotation of the drive unit.