A washing machine with an improved structure capable of effectively fixing a diaphragm on a tub includes: a cabinet including a first opening; a tub positioned in the inside of the cabinet, and including a second opening and a protruding rib protruding toward a center of the second opening; a drum rotatably positioned in the inside of the tub, and including a third opening; and a diaphragm connecting the first opening with the second opening, and including a first flange and a second flange that are coupled with the tub, wherein the first flange is fixed on an outer surface of the tub and the second flange is coupled with the protruding rib such that an interval between the diaphragm and the third opening is maintained uniform.