A dishwasher includes a tub, a spray arm, and a spray arm. The spray arm includes an arm body that defines a plurality of channels that are partitioned from each other and that are configured to carry washing water and a plurality of spray holes configured to discharge washing water from the plurality of channels toward the washing objects. The spray arm further includes a chamber disposed vertically below the arm body and configured to communicate with the plurality of channels; a channel guider configured to supply washing water from the spray arm holder to the chamber; and a channel switch unit accommodated in the chamber and configured to open and close at least a portion of the plurality of channels.