strongest thread tension and the left end shows the weakest one and the set position is displayed with the reverse white black indication the numeral 35 represents 34 automatic 34 mode for setting a predetermined thread tension with respect to stitching conditions a selection detecting point 9f of the transparent touch panel 9 is c 3 in fig4 and upon actuation a signal for designating the automatic thread tension is output the electric thread tension device is set to the automatic thread tension and the indication 34 automatic 34 35 disposed at the center of the level meter 36 is shown in reverse white black the numeral 36 denotes the 34 34 indication the corresponding selection detecting point 9g of the transparent touch panel 9 is c 4 of fig4 for outputting a signal to set the thread tension to be strong and the indication 34 of the liquid crystal is moved rightwards in succession by operating the electric thread tension device the numeral 37 denotes the 34 34 indication the corresponding selection detecting point 9e of the transparent touch panel 9 is c 2 of fig4 for outputting a signal to set the thread tension to be weak and the indication 34 of the liquid crystal is moved leftwards in succession by operating the electric thread tension device when the alteration of the thread tension is finished and if operating the selection detecting point of the transparent touch panel 0 on 34 thread tension 34 mode 133 a signal is output for designating return to 34 set 34 mode indication on the screen the set value of the thread tension is stored in the function controlling information memory 24 the 2nd ram in fig1 the numeral 38 designates 34 amplitude 34 the corresponding selection detecting part.