A setup method of top tension devices which have adjusting members (8,9) for applying electrically controllable tension to yarns and are provided on a flat knitting machine, being characterized in that a measuring step, performed outside a flat knitting machine, for measuring and storing an input value for each yarn to an adjusting member for applying a desired tension to said each yarn is performed, wherein said each yarn (10is fed to and drawn by a drawing member through a tension sensor and the adjusting member, wherein the drawing member, the tension sensor, and the adjusting member are provided out of the flat knitting machine, wherein said input value to the adjusting member is measured with a dedicated measuring device when the tension to said each yarn is a desired value, and wherein said input value is stored, that a step for storing elements (11,40,42) that contact or influence said each yarn in each yarn feeding route from a top tension device to a carrier of said each yarn and comprise: species of yarn feeding objects (40,42), at an upper stream position of the carrier along a direction of yarn feeding, to which said each yarn is fed by the top tension device; the number of eyelets through which said each yarn passes in each yarn feeding route; and a degree of bending said each yarn by the eyelets in said each yarn feeding route is performed, and that a setup step for correcting said input value on the basis of the elements (11,40,42) in order to transform said input value to a setup value for the adjusting members in each yarn feeding route and applying the setup value to the adjusting member in each yarn feeding route by a controller in the flat knitting machine is performed. a measuring step, performed outside a flat knitting machine, for measuring and storing an input value for each yarn to an adjusting member for applying a desired tension to said each yarn is performed, wherein said each yarn (10is fed to and drawn by a drawing member through a tension sensor and the adjusting member, wherein the drawing member, the tension sensor, and the adjusting member are provided out of the flat knitting machine, wherein said input value to the adjusting member is measured with a dedicated measuring device when the tension to said each yarn is a desired value, and wherein said input value is stored, that a step for storing elements (11,40,42) that contact or influence said each yarn in each yarn feeding route from a top tension device to a carrier of said each yarn and comprise: species of yarn feeding objects (40,42), at an upper stream position of the carrier along a direction of yarn feeding, to which said each yarn is fed by the top tension device; the number of eyelets through which said each yarn passes in each yarn feeding route; and a degree of bending said each yarn by the eyelets in said each yarn feeding route is performed, and that a setup step for correcting said input value on the basis of the elements (11,40,42) in order to transform said input value to a setup value for the adjusting members in each yarn feeding route and applying the setup value to the adjusting member in each yarn feeding route by a controller in the flat knitting machine is performed.