Surface roughness of polished silicon wafers was observed by reflection electron microscopy (REM). Small steps were clearly resolved as fringe patteren, and rather rough steps of 1.2-1.6 nm in height and 200-500 nm in interval were observed as dark and bright bands. The Si-SiO2 interface was also observed by REM. REM has been confirmed as an effective means of observing both the silicon surface and the Si-SiO2 interface.