PURPOSE: To make three lead wires to be always in a constant arranging state at the end of winding by controlling a motor thrusting at least one foil among two dielectric foils and to conductor foils so as to decrease the tension as number of times of winding increases thereby making the winding tension of each layer constant.

CONSTITUTION: Tension arms 5a, 5b are provided between a winding core 10 and reels 2a, 2b supplying the dielectric foils 1a, 1b and rotary encoders 8a, 8b generating a digital signal in response to the tension are fitted to the shaft. A control circuit 20 receives the pulse signal of a pulse generator 12 driving a stepping motor 11 of the winding core 10 and a digital signal from the rotary encoders 8a, 8b and is provided with a frequency divider 21, a counter circuit 22 and comparators 23a, 23b, and when the count of the counter circuit 22 is larger than the digital signal of the rotary encoder, an output generated from the comparator controls the pulse generators 24a, 24b, the pulse output drives stepping motors 7a, 7b for thrusting, which are controlled that the tension is weakened as the winding is progressed.