A drum washing machine has a cabinet including an opening formed at a front wall of the cabinet to allow laundry to be put into or taken out of the cabinet, a door to open or close the opening of the cabinet, and an opening/closing guide mechanism connected between the cabinet and the door to guide the door downwardly when opening the door such that a front surface of the door is upwardly directed, and to guide the door upwardly moved when closing the door such that the door is vertically openable and closable. The door of the drum washing machine can be easily opened even where the washing machine is installed in a limited space. The door can also be used as a laundry holder in an opened state.