Provided is a rail device for a dishwasher, including a guide main body part; an upper support roller part coupled to one side of the guide main body part to be rotatable with respect to a central axis; a lower support roller part coupled to one side of the guide main body part to be rotatable with respect to a central axis; a guide rail part extendedly formed along the sliding direction with one side inserted into a space between the upper support roller part and the lower support roller part; and a rack roller part having one side inserted into the guide rail part and the other side coupled to one surface inside the main body of the dishwasher or coupled to a sliding basket.