For the design of tidal current turbine, there are hydrodynamic design and structural design, which should be considered. The design methods must be satisfied with the performance and structural safety for its feasibility. Most of the tidal current turbine requires hydrodynamic design in order to improve the efficiency and performance. It is necessary to have a clear understanding of the characteristics of the blade adjacent flow field. The casing and shaft of tidal current turbine driving part, which is affected from flow field, needs to be designed and evaluated for structure safety to withstand all the harsh conditions of the sea. In this study, driving part of tidal current turbine was investigated by evaluating structural safety with analysis of one way fluid structure interaction (FSI) analysis. The fluid structure interaction analysis of driving part was conducted for different shapes of driving part with same 15kW-class tidal current turbine blade. For conducting reliable evaluation of structural safety, the surface load(pressure) of the tidal current turbine driving part is obtained from CFD analysis for initial condition of FSI analysis.