Gels are expected as the biomaterial of the human body such as our cartilages because of the improvement of the mechanical strength and their extremely low friction coefficient. The friction behavior of gels is different from hard and dry materials like metals, plastics and ceramics. In this study, we focus on the dynamic frictional interface of hydrogels and aim to develop a new apparatus with a polarization microscope for observation. The comparison between direct observation and measurement of friction coefficient will become a foothold to elucidate distinctive frictional phenomena that can be seen in soft and wet materials.