Eco-friendly and sustainable seaweed biomass energy have been under the spotlight as the future of renewable energy. However, seaweed culture is primarily conducted inshore, with the research on offshore culture still in an early stage. For massive biomass production, a systematic engineering approach is required to devise offshore seaweed culture facilities rather than the conventional empirical ones. To establish the fundamental behavior of seaweed culture facilities, the dynamic characteristics of a seaweed culture facility were analyzed in the study. For this purpose, numerical analyses of the seaweed culture facility (a frame type) were carried out by using the hydrodynamic simulation program ANSYS-AQWA. For the analysis, environmental loads were considered using the wave spectra and co-linear current; mooring variables were selected as parameters; and time domain analyses were carried out to acquire the time series responses and eventually the dynamic characteristics. Finally, the mooring performance was evaluated. It was found that the motion could be controlled by adjusting the buoyancy and mooring slope.