In this paper, we will discuss the concept of combined utilization of offshore wind and wave energy in terms of both tank test and numerical simulation. There are some possibility that combined utilization of ocean renewable energies can avoid some disadvantages that single utilization of them may have, such as cost problem associated with the stability of power and power supply. In this study, we focus on the motion of an offshore wind turbine in waves associated to wave energy converters, are installed in the same area in order to improve its motion by reducing the effect of incident waves. We carried out wave tank test and numerical simulation, and investigated the motion of wind turbine in waves. In addition, numerical simulation allows to visualize the wave fields around those devices. Appropriate arrangement of them is discussed for the most efficient utilization of offshore wind and wave energy.