Provided is a detergent feeding device including a detergent box provided with a detergent accommodating part having an opening part; an opening and closing member; a detergent box housing accommodating the detergent box; a dispenser to supply water to the detergent box; a first water supply tube supplying water to the dispenser; a second water supply tube connected to the detergent box housing; and an opening unit connected to an outlet of the second water supply tube, wherein the opening unit is moved by water pressure of the water supplied from the second water supply tube to push the opening and closing member to open the opening part of the detergent accommodating part.