This study developed a real-time wave prediction system by using SWAN (Simulating WAves Nearshore) with the data of hourly analyzed atmospheric GPV (Grid Point Value). The validity of this system was carried out by comparing the predictions with observations from NOWPHAS (Nationwide Ocean Wave information network for Ports and HArbourS) during one month of December, 2007. The predicted wave heights and periods well corresponded to the observed ones. By using this system, wave situations at present and short-term future can be estimated for locations where there are no wave observation equipments.