A washing machine comprising: a cabinet; a tub disposed inside the cabinet to accommodate wash water; a drain pump disposed at a lower side of the tub to drain the wash water contained in the tub; a first drain hose (100, 200) connecting the tub to the drain pump to allow the wash water contained in the tub to be introduced into the drain pump; and a second drain hose guiding the wash water, which is introduced into the drain pump, to outside the cabinet, wherein the first drain hose (100, 200) comprises: a passage (110, 120, 130) allowing wash water and air to pass therethrough; and a cross section reducing part (150, 250) configured to reduce a cross section of the passage to disturb a flow of the air passing through the passage, characterized in that the first drain hose further comprises: a first connection part connected to the tub and a second connection part connected to the drain pump and a wrinkled part provided between the first connection part and the second connection part, wherein the cross section reducing part is formed at a position nearer to the second connection part than the first connection part and between the wrinkled part and the second connection part; whereby the cross section reducing part (150, 250) either: has a concave form obtained by concaving a portion of an upper side of the first drain hose in a radial direction of the first drain hose, or is provided by a partition provided by extending an inner circumferential surface of an upper of the first drain hose, the partition including, with respect to a direction of the wash water flowing from the first connection part to the second connection part, a first inclined part, which is formed in an inclined manner to decrease a cross section of the first drain hose, a second inclined part, which is formed to an approximate opposite side to an inclination of the first inclined part in an inclined manner to increase a cross section of the first drain hose, and a planar surface formed between the first inclined part and the second inclined part. a cabinet; a tub disposed inside the cabinet to accommodate wash water; a drain pump disposed at a lower side of the tub to drain the wash water contained in the tub; a first drain hose (100, 200) connecting the tub to the drain pump to allow the wash water contained in the tub to be introduced into the drain pump; and a second drain hose guiding the wash water, which is introduced into the drain pump, to outside the cabinet, wherein the first drain hose (100, 200) comprises: a passage (110, 120, 130) allowing wash water and air to pass therethrough; and a cross section reducing part (150, 250) configured to reduce a cross section of the passage to disturb a flow of the air passing through the passage, a passage (110, 120, 130) allowing wash water and air to pass therethrough; and a cross section reducing part (150, 250) configured to reduce a cross section of the passage to disturb a flow of the air passing through the passage, characterized in that the first drain hose further comprises: a first connection part connected to the tub and a second connection part connected to the drain pump and a wrinkled part provided between the first connection part and the second connection part, wherein the cross section reducing part is formed at a position nearer to the second connection part than the first connection part and between the wrinkled part and the second connection part; whereby the cross section reducing part (150, 250) either: has a concave form obtained by concaving a portion of an upper side of the first drain hose in a radial direction of the first drain hose, or is provided by a partition provided by extending an inner circumferential surface of an upper of the first drain hose, the partition including, with respect to a direction of the wash water flowing from the first connection part to the second connection part, a first inclined part, which is formed in an inclined manner to decrease a cross section of the first drain hose, a second inclined part, which is formed to an approximate opposite side to an inclination of the first inclined part in an inclined manner to increase a cross section of the first drain hose, and a planar surface formed between the first inclined part and the second inclined part. has a concave form obtained by concaving a portion of an upper side of the first drain hose in a radial direction of the first drain hose, or is provided by a partition provided by extending an inner circumferential surface of an upper of the first drain hose, the partition including, with respect to a direction of the wash water flowing from the first connection part to the second connection part, a first inclined part, which is formed in an inclined manner to decrease a cross section of the first drain hose, a second inclined part, which is formed to an approximate opposite side to an inclination of the first inclined part in an inclined manner to increase a cross section of the first drain hose, and a planar surface formed between the first inclined part and the second inclined part.