of illustration the variable mark 43 is indicated by an 34 x 34 in fig2 in actuality however this mark 43 like the scale markings 42 is shown as a dot on the monitor furthermore the distance the variable mark 43 moves from the central scale marking 42a and the pitch at which the variable mark 43 moves each time may be displayed in numerical values on the monitor 17 the variable mark 43 is moved one pitch at a time in the plus or minus direction on the scale line 41 when the increase conversion switch s2 or the decrease conversion switch s3 is pressed the plus direction is the direction shown by arrows a and the minus direction is the direction shown by arrows b in fig2 the pitch by which the variable mark 43 moves each time can be changed to for example 2 5 microns 5 microns etc by adjusting the increase conversion switch s2 or the decrease conversion switch s3 accordingly as shown in fig2 the bend in the wire can be more accurately measured by operating the increase conversion switch s2 or the decrease conversion switch s3 so that the variable mark 43 is moved on the scale line 41 until it comes onto the measurement point of the wire 3 in the present invention as described above a bend in the wire loop is measured at the bonding station by viewing the image of the wire loop on a monitor as.