A laundry machine comprising: a tub to receive wash water, wherein the tub comprises a tub front and a tub rear, wherein the tub rear comprises a rear-gasket-outer-circumference-coupling part formed in an inner circumference of a rear surface of the tub rear and extending, bent, backwards of the tub rear; a drum rotatably placed in the tub; a shaft connected with the drum; a bearing housing to support the shaft; a tub back comprising a rim part extending in a rear direction of the tub rear, wherein the tub back is coupled to the bearing housing at a front part of the bearing housing, wherein the tub back comprises a seating part formed in the rim part and extending in a radial direction partially or all along a circumference of the rim part and wherein the tub back comprises a plurality of ribs (134, 135) on a rear surface and wherein the ribs (134, 135) comprises radially extended ribs and circumferentially extended ribs and wherein a plurality of coupling bosses are formed in the radially extended ribs and circumferentially extended ribs for coupling the bearing housing to the tub back; a rear gasket connected between the tub back and the tub, wherein the rear gasket comprises a tub rear coupling part formed in an outer circumference of the rear gasket and being surroundingly coupled to the rear-gasket-outer-circumference-coupling part, and a tub back coupling part formed in an inner circumference of the rear gasket and coupled to the seating part, wherein a first inserting recess is formed in an outer circumferential surface of the tub rear coupling part, corresponding to the bent portion of the rear gasket-outer-circumference-coupling part, and a second inserting recess is formed in an outer circumferential surface of the tub back coupling part, corresponding to a recess formed between the seating part and a seating rib of the rim part, a suspension unit configured to reduce vibration of the drum, a first coupling ring fastening the tub rear coupling part of the rear gasket to the rear-gasket-outer-circumference coupling part of the tub rear, wherein the first coupling ring presses the tub rear coupling part of the rear gasket towards the center of the tub rear; and a second coupling ring fastening the tub back coupling part of the rear gasket to a seating part of the rim part of the tub back, wherein the second coupling ring presses the tub back coupling part of the rear gasket towards the center of the tub back to couple the rear gasket to the tub back, wherein the first and second coupling rings (253a, 253b) are inserted in the first and second inserting recesses (251a, 251b), respectively. a tub to receive wash water, wherein the tub comprises a tub front and a tub rear, wherein the tub rear comprises a rear-gasket-outer-circumference-coupling part formed in an inner circumference of a rear surface of the tub rear and extending, bent, backwards of the tub rear; a drum rotatably placed in the tub; a shaft connected with the drum; a bearing housing to support the shaft; a tub back comprising a rim part extending in a rear direction of the tub rear, wherein the tub back is coupled to the bearing housing at a front part of the bearing housing, wherein the tub back comprises a seating part formed in the rim part and extending in a radial direction partially or all along a circumference of the rim part and wherein the tub back comprises a plurality of ribs (134, 135) on a rear surface and wherein the ribs (134, 135) comprises radially extended ribs and circumferentially extended ribs and wherein a plurality of coupling bosses are formed in the radially extended ribs and circumferentially extended ribs for coupling the bearing housing to the tub back; a rear gasket connected between the tub back and the tub, wherein the rear gasket comprises a tub rear coupling part formed in an outer circumference of the rear gasket and being surroundingly coupled to the rear-gasket-outer-circumference-coupling part, and a tub back coupling part formed in an inner circumference of the rear gasket and coupled to the seating part, wherein a first inserting recess is formed in an outer circumferential surface of the tub rear coupling part, corresponding to the bent portion of the rear gasket-outer-circumference-coupling part, and a second inserting recess is formed in an outer circumferential surface of the tub back coupling part, corresponding to a recess formed between the seating part and a seating rib of the rim part, a suspension unit configured to reduce vibration of the drum, a first coupling ring fastening the tub rear coupling part of the rear gasket to the rear-gasket-outer-circumference coupling part of the tub rear, wherein the first coupling ring presses the tub rear coupling part of the rear gasket towards the center of the tub rear; and a second coupling ring fastening the tub back coupling part of the rear gasket to a seating part of the rim part of the tub back, wherein the second coupling ring presses the tub back coupling part of the rear gasket towards the center of the tub back to couple the rear gasket to the tub back, wherein the first and second coupling rings (253a, 253b) are inserted in the first and second inserting recesses (251a, 251b), respectively.