To develop early tsunami warning system utilizing ocean radars, the evaluation of the variety of measuring coverage and data accuracy is indispensable in real oceans. The field observation was carried out at 5 minutes interval with two digital beam forming ocean radars with VHF band from 2012 to 2014 in the sea of Enshu. The high data acquisition areas are found in the extent of 17km off the coast on a hill site and of 13km on a low ground site. The measured current by the ocean radar were well correlated with that by the current-meter in the depth of 2m near the coast with the correlation coefficient of ~0.6. It is inferred that the main factor of difference in both data sets was due to the presence of wind-driven current through the multi-regression analysis with both current data and wind data. In addition, the order of the temporal current deviations as to the representative time-scale of one hour is about 5cm/s under the ordinary sea conditions, which suggest that ocean radars could sufficiently detect the current deviation due to grant tsunami.