In the present study, the primary energy conversion performance of an oscillating water column (OWC) was evaluated through experimental tests and numerical simulations. The experimental tests were performed at an ocean basin located in Korea Research Institute of Ships and Ocean Engineering (KRISO), Korea. A 1/4 scaled OWC chamber model with an orifice to account for the turbine effect was set up at the 3-dimensional basin, and regular wave tests were performed at various incident wave periods. The water surface level inside the chamber, the differential pressure between before and after the orifice, and the airflow speed through the orifice were measured. Computational fluid dynamics (CFD) analysis was performed using the Star-CCM+ commercial software to analyze the performance of the OWC for the same model that was used in the experiment. Detailed flow fields were discussed based on the CFD results, and the numerical and experimental results were compared. The validation results showed good agreement.