We present the result of near-infrared and optical observations of the BL Lac object S5 0716 + 714 carried out by the KANATA telescope .
S5 0716 + 714 has both a long term high-amplitude variability and a short-term variability within a night .
The shortest variability ( microvariability ) time-scale is important for understanding the geometry of jets and magnetic field , because it provides a possible minimum size of variation sources .
Here , we report the detection of 15-min variability in S5 0716 + 714 , which is one of the shortest time-scales in optical and near-infrared variations observed in blazars .
The detected microvariation had an amplitude of 0.061 { \pm } 0.005 mag in V band and a blue color of \Delta ( V - J ) = -0.025 { \pm } 0.011 .
Furthermore , we successfully detected an unprecedented , short time-scale polarimetric variation which correlated with the brightness change .
We revealed that the microvariation had a specific polarization component .
The polarization degree of the variation component was higher than that of the total flux .
These results suggest that the microvariability originated from a small and local region where the magnetic field is aligned .