One of the promising cosmological probes in the next decades is the CMB polarization. While CMB temperature anisotropies have been already measured very precisely, CMB polarization, in particular a twisting pattern in the polarization map (B mode) is not well measured. The detection of B mode at more than degree angular scale opens new window into the inflationary universe and high energy physics beyond the standard model. Precise polarization data also enables us to measure gravitational lensing of CMB which is a key probe to understand the properties of neutrinos, dark matter and dark energy. In this talk, I will present analysis of the gravitational lensing and cosmic birefringence measurements with CMB polarization data taken from BICEP2/Keck Array experiments. I will also talk about synergy between CMB experiments and galaxy surveys such as the galaxy-lensing cross correlation with Subaru-Hyper Suprime Cam and CMB experiments, and delensing B mode with mass tracers.