A washing machine including a cabinet having a first introduction port, a tub, which is provided in the cabinet and which has a second introduction port that is concentrically positioned with respect to the first introduction port, a cabinet door attached to the cabinet to open and close the first introduction port, a tub door attached to the tub to open and close the second introduction port, and a lock-releasing unit, which is attached to the cabinet to release a locked state of the cabinet door and the tub door.