A detergent feeding device comprising: a detergent box including a detergent accommodating part (130,140) arranged to receive a liquid detergent or a powder detergent, a detergent box housing accommodating the detergent box, the detergent accommodating part (130, 140) having an opening part formed at the rear end thereof for allowing the liquid detergent or the powder detergent to be discharged into the detergent box housing; an opening and closing member movably provided at the detergent box to selectively open and close the opening part of the detergent accommodating part (130, 140); a dispenser disposed above the detergent box housing to supply water to the detergent box; a first water supply tube connected to the dispenser and arranged to supply water to the dispenser; a second water supply tube connected to the detergent box housing; an opening unit (211, 214, 215) provided on the detergent box housing, the opening unit (211, 214, 215) being connected to an outlet of the second water supply tube, wherein the opening unit (211,214,215) is moveable by water pressure of the water supplied from the second water supply tube to cause the opening and closing member to open the opening part of the detergent accommodating part (130, 140), characterised in that the detergent feeding device further comprises: a fixing rib protruding from the opening and closing member; a support rib (127, 129) to connect a side wall part (123,124) of the detergent box to a partition side wall part of the detergent box; an elastic member installed on the support rib (127, 129) and elastically deformed by the fixing rib; a guide part protruding from the dispenser to the detergent box; and an auxiliary rib protruding from the opening and closing member to selectively contact the guide part; wherein, when the detergent box is withdrawn from the detergent box housing, the auxiliary rib is moved downward along the guide part, the opening and closing member is rotated to an original position thereof by the moving of the auxiliary rib so as to close the opening part of the detergent accommodating part (130,140). a detergent box including a detergent accommodating part (130,140) arranged to receive a liquid detergent or a powder detergent, a detergent box housing accommodating the detergent box, the detergent accommodating part (130, 140) having an opening part formed at the rear end thereof for allowing the liquid detergent or the powder detergent to be discharged into the detergent box housing; an opening and closing member movably provided at the detergent box to selectively open and close the opening part of the detergent accommodating part (130, 140); a dispenser disposed above the detergent box housing to supply water to the detergent box; a first water supply tube connected to the dispenser and arranged to supply water to the dispenser; a second water supply tube connected to the detergent box housing; an opening unit (211, 214, 215) provided on the detergent box housing, the opening unit (211, 214, 215) being connected to an outlet of the second water supply tube, wherein the opening unit (211,214,215) is moveable by water pressure of the water supplied from the second water supply tube to cause the opening and closing member to open the opening part of the detergent accommodating part (130, 140), characterised in that the detergent feeding device further comprises: a fixing rib protruding from the opening and closing member; a support rib (127, 129) to connect a side wall part (123,124) of the detergent box to a partition side wall part of the detergent box; an elastic member installed on the support rib (127, 129) and elastically deformed by the fixing rib; a guide part protruding from the dispenser to the detergent box; and an auxiliary rib protruding from the opening and closing member to selectively contact the guide part; wherein, a fixing rib protruding from the opening and closing member; a support rib (127, 129) to connect a side wall part (123,124) of the detergent box to a partition side wall part of the detergent box; an elastic member installed on the support rib (127, 129) and elastically deformed by the fixing rib; a guide part protruding from the dispenser to the detergent box; and an auxiliary rib protruding from the opening and closing member to selectively contact the guide part; wherein, when the detergent box is withdrawn from the detergent box housing, the auxiliary rib is moved downward along the guide part, the opening and closing member is rotated to an original position thereof by the moving of the auxiliary rib so as to close the opening part of the detergent accommodating part (130,140). the auxiliary rib is moved downward along the guide part, the opening and closing member is rotated to an original position thereof by the moving of the auxiliary rib so as to close the opening part of the detergent accommodating part (130,140).