A washing machine is disclosed. The washing machine includes a cabinet having a first introduction port, a tub, which is disposed in the cabinet and which has a second introduction port concentrically positioned with respect to the first introduction port, a cabinet door mounted on the cabinet so as to open and close the first introduction port, a tub door mounted on the tub so as to open and close the second introduction port, and a lock-releasing unit for releasing the locked state of the tub door when the cabinet door is opened.