A preliminary validation of surface information extraction is conducted from ERS-SAR image mode data in the coast areas of Japan. In this study, we investigated the energy of simulated SAR spectrum at different wind speed using nonlinear wave-SAR imaging mechanism, derived the criteria to differentiate swell from wind waves, and accordingly processed SAR images containing swell and wind waves in different way respectively. Wave information such as wave direction and significant wave heights which are retrieved from 66 match-ups agrees well with that from in-situ NOWPHAS wave gauge data. The relation between cutoff wavelength and the root of wave height is in good proportional relation. This study demonstrates that the SAR image mode data can be used for the observation of ocean waves in coastal areas.