PURPOSE: To exactly measure a driving pulse width by calculating the driving pulse width of a step motor from the timing data of the min. value and max. value of the level data which samples the detection signal of leak magnetic fluxes.

CONSTITUTION: The leak magnetic fluxes during motor driving of the electronic timepiece are converted by a detecting coil 5 to electric signals which are then amplified 6. The leak magnetic flux detecting waveforms subjected to the influence of wheel trains are binarized by a window comparator 7 to generate 15 a sampling clock. The leak magnetic flux detecting waveform which is the output of an amplifier 6 is converted 16 to a digital value in synchronization with the clock. The digital value is stored together with the count value of a counter 18 in an FIFO 20. The data of the detected level stored in the FIFO 20 and the count value of this time are read out by a CPU 22 and the max. value and min. value of the detected level are retrieved. The driving pulse width is calculated from this count value, by which the driving pulse width is exactly measured without receiving the influence of the wheel trains and step motors.