  The bright radio source S5 0716+714, that is usually classified as BL Lac
object, is one of the most intensively studied. S5 0716+714 demonstrates
extremely peculiar properties such as the shortest time-scale of optical and
polarimetric variations observed in blazars. In given paper, the results of
9-hour polarimetric monitoring of S5 0716+714 with the $\sim$70-second
resolution, carried out by the 6-m telescope BTA of SAO RAS, are presented. The
observation data analysis reveals the variability both in total and polarized
light on the 1-1.5-hour time-scale. Since polarization is generated by plasma
motion in the magnetic field, the variations of polarization vector are bounded
with the magnetic field configuration and the average time-scales specify the
size of the emitting region, unresolved directly. We suggest a processed
numerically model of polarization in the jet with the precessing helical
magnetic field. Fitting the model discovers that observed short-term variations
with the complicated trajectory of polarization vector could be induced by the
magnetic field precession with the period $T \approx 15$ days.
