  We have obtained simultaneous and continuous photo-polarization observations
of the blazar BL Lacertae in optical and near-infrared (NIR) bands during a
historical outburst from 2020 to 2021. In total, fourteen nights of
observations were performed where ten observations show microvariability on
timescales of a few minutes to several hours. This suggests a compact emission
region, and the timescales are difficult to explain by a one-zone shock-in-jet
model. Moreover, we found significant differences in the polarization degree
(PD) and angle between optical and NIR bands. Nine nights showed a PD in the
optical band that is greater than or equal to that in the NIR band, which can
be explained by either a shock-in-jet model or the Turbulent Extreme Multi-Zone
(TEMZ) model. On the other hand, five nights showed higher PD in a NIR band
than an optical band, which cannot be explained by simple shock-in-jet models
nor the simple TEMZ model. The observed timescales and wavelength dependency of
the PD and polarization angle suggest the existence of complicated multiple
emission regions such as an irregular TEMZ model.
