A dishwasher includes a tub. The dishwasher further includes a spray arm that includes a main arm and an auxiliary arm. The dishwasher further includes a fixed gear part that is connected to the tub, that is configured to rotatably support the main arm, and that includes teeth along an outer circumferential surface of the fixed gear part. The dishwasher further includes a rotating gear part that is connected to the main arm and that is configured to rotate and engage the teeth of the fixed gear part based on rotation of the main arm. The dishwasher further includes a link unit that is connected to the rotating gear part, the main arm, and the auxiliary arm, that is configured to move based on rotation of the rotating gear part, and that is configured to guide reciprocation of the auxiliary arm through the predetermined arc.