A sewing needle bar (5; 105) comprising: a tubular needle bar body (10; 110) including a small-diameter portion which is provided at a lower end of the needle bar body and which has a hole opened along an axis line of the needle bar body and a large-diameter portion which is continually provided on an upper side of the small-diameter portion and which has a hole opened larger in diameter than the hole of the small-diameter portion and along the axis line of the needle bar body; and a joint which secures a sewing needle (60; 160), characterized by: a cylindrical sleeve which is inserted in the hole of the large-diameter portion of the needle bar body and which has an opening for placing a ball; a cam shaft (30; 130) including a disc-shaped portion which is placed on an upper surface of the small-diameter portion in the needle bar body in a rotatable manner and which has an outer diameter larger than a diameter of the hole of the small-diameter portion, a spindle-shaped upper shaft which is formed upwardly from the upper surface of the disc-shaped portion and remains inserted in the sleeve and whose outer circumferential surface has a clockwise helical groove, and a spindle-shaped lower shaft which is formed downwardly from a lower surface of the disc-shaped portion and remains inserted in the hole of the small-diameter portion of the needle bar body and which protrudes downwardly from a lower end of the small-diameter portion; a ball which is placed in the opening of the sleeve and which come into engagement with the groove of the upper shaft; wherein the joint is secured to the lower shaft while the small-diameter portion of the needle bar body are sandwiched between the joint and the disc-shaped portion, and wherein changes occur in relative positions of the ball in the groove as a result of the needle bar body (10; 110) being vertically moved while a portion of the sleeve protruding upward from the needle bar body remains fixed, whereupon the cam shaft (30; 130) and the joint rotate. a tubular needle bar body (10; 110) including a small-diameter portion which is provided at a lower end of the needle bar body and which has a hole opened along an axis line of the needle bar body and a large-diameter portion which is continually provided on an upper side of the small-diameter portion and which has a hole opened larger in diameter than the hole of the small-diameter portion and along the axis line of the needle bar body; and a joint which secures a sewing needle (60; 160), a small-diameter portion which is provided at a lower end of the needle bar body and which has a hole opened along an axis line of the needle bar body and a large-diameter portion which is continually provided on an upper side of the small-diameter portion and which has a hole opened larger in diameter than the hole of the small-diameter portion and along the axis line of the needle bar body; and a joint which secures a sewing needle (60; 160), a cylindrical sleeve which is inserted in the hole of the large-diameter portion of the needle bar body and which has an opening for placing a ball; a cam shaft (30; 130) including a disc-shaped portion which is placed on an upper surface of the small-diameter portion in the needle bar body in a rotatable manner and which has an outer diameter larger than a diameter of the hole of the small-diameter portion, a spindle-shaped upper shaft which is formed upwardly from the upper surface of the disc-shaped portion and remains inserted in the sleeve and whose outer circumferential surface has a clockwise helical groove, and a spindle-shaped lower shaft which is formed downwardly from a lower surface of the disc-shaped portion and remains inserted in the hole of the small-diameter portion of the needle bar body and which protrudes downwardly from a lower end of the small-diameter portion; a disc-shaped portion which is placed on an upper surface of the small-diameter portion in the needle bar body in a rotatable manner and which has an outer diameter larger than a diameter of the hole of the small-diameter portion, a spindle-shaped upper shaft which is formed upwardly from the upper surface of the disc-shaped portion and remains inserted in the sleeve and whose outer circumferential surface has a clockwise helical groove, and a spindle-shaped lower shaft which is formed downwardly from a lower surface of the disc-shaped portion and remains inserted in the hole of the small-diameter portion of the needle bar body and which protrudes downwardly from a lower end of the small-diameter portion; a ball which is placed in the opening of the sleeve and which come into engagement with the groove of the upper shaft; wherein the joint is secured to the lower shaft while the small-diameter portion of the needle bar body are sandwiched between the joint and the disc-shaped portion, and wherein changes occur in relative positions of the ball in the groove as a result of the needle bar body (10; 110) being vertically moved while a portion of the sleeve protruding upward from the needle bar body remains fixed, whereupon the cam shaft (30; 130) and the joint rotate.