PURPOSE: To enable the accurate detection of the residual quantity of electric wire without the influence of variablity of a resistance value by a method wherein an electric resistance is measured at each time of completion of winding and the resistance value of the electric wire of the length necessary for one winding is calculated based on the average of the measured resistance values and the calculated value is compred with each measured value.

CONSTITUTION: The electric resistance r0 of an electric wire 1 of the section held by a chuck 8 and a chuck 15 is measured and is stored in a microcomputer. Next, the resistance r1 between a new front end and a terminal is measured and R1=r0-r1 is obtained. Then, the electric resistance Ri or (i) times is measured at completion of winding operation of each time and is stored in a computer which calculates the average of variation of resistance value Ri=ri-1-ri. Based on this average value, the resistance value of an electric wire of the length necessary for one winding is calculated and this calculated value is compared with the measured value ri or each time to determine whether the residual quantity of a wire at measurement of (i) times has the length necessary for one winding or not. Consequently, the accurate detection of residual quantity of an electric wire can be done without the influence of the variability of resistance value per length of wire of each manufacturing lot.