The propulsion method of the aquatic life is a result of optimization by evolution. Research of the propulsion method is useful for the design of robot that operates efficiently, for example swimming-robot etc. This study is about a loath that swims bending whole body. Our purpose of research is to clarify its swimming mechanism through flow field analysis. We analyzed the three-dimensional flow field around the loath using stereoscopic PIV, about both horizontal cross section and vertical section. As a result, we captured three-dimensional flow field and vortex structure around the loath.
