PURPOSE: To minimumize the variation in exposed length of a conductor due to unevenness of attached intervals of an insulating tape by calculating a position of the conductor corresponding to the intermediate portion of the insulating tape on the basis of the calculated length so as to cut the conductor at the position.

CONSTITUTION: A detection signal of a sensor 14 is supplied to a counter 22. A pulse quantity until the fore end of a succeeding tape 2 passes after the rear end of an insulating tape 2 passes is counted by using the detection signal of the sensor 14 as a trigger and reset signal, thus controlling a drive motor M and a solenoid valve 25. The sensor 14 detects the passing of the rear end of the insulating tape 2A, a semi-product cable 3 is fed by a distance X, which is defined by an equation: X=a+b/2, wherein (a) represents a distance between the sensor 14 and a cutter 16; and (b) a relationship between the insulating tape 2A and succeeding insulating tape 2B constituting one tape electric wire, and then, the cutter 16 is operated so that a continuous tape electric wire 15 can be cut in the central portion of a conductor 1 between the tapes 2A and 2B. Therefore, variation in length projected from both ends of the conductor 1 can be dispersed to the adjacent tape electric wires 2.