This paper presents the characteristics of wave conditions, wave energy absorption, response of hull-motion and wave height dissipation based on the results of the open sea tests. 0.5–1.0m of significant wave height and 6–7 seconds of significant wave period appear the most predominant, and average wave energy is estimated 4.88kW/m around the test site. Average power output for the test is approximately 6kWh and the maximum total energy efficiency is around 15% that is ranging from 6–7 seconds of significant wave period. Slow drift oscillation of hull was observed motion in surge, sway and yaw and the value of its amplitude almost equal to estimated values in design stage. Then the mean value of transmission coefficient is about 0.8 under 8.0 seconds of significant wave period. We are considering that the results of the tests should be useful for optimum design of an offshore floating type wave power device.Copyright © 2002 by ASME