It is quite likely that a complex turbulent flow field and large pressure fluctuation induced by separation vortex shed from the intrados of the elbows are seemed to appear in the cold leg piping of the primary cooling system of Japan Sodium-cooled Fast Reactor. This study researched the influence of the inflow condition upon the flow separation especially in the 3rd elbow. In this study, the inflow condition to the 3rd elbow was imposed by changing the distance between the 2nd and 3rd elbows from 6.4D (original design) to 9.4D. The visualization experiment showed that the flow separation appeared in the intrados of the 3rd elbow as was the case with the original design and the separated regions became larger than that in the original one. This is because a swirling flow observed at the inlet of the 3rd elbow became weaker than that in the original case.