This paper presents a parametric study on oscillating water column (OWC) wave energy converter (WEC). The OWC is being planned to be placed on a breakwater in isolated islands remote from the land. Both of numerical analysis and model experiment were utilized for deciding a proper conceptual design that covers the purpose. Various design parameters including configurations and dimensions were evaluated through the numerical analysis, which is based on a potential flow theory, and then several design concepts were selected as candidates. The model experiment using a 2D wave flume was performed to evaluate effects of design parameters and compare performances for the candidates. Based on overall results from the numerical analysis and the model experiment, a conceptual design of the OWC WEC applicable to a breakwater was selected.