In order to apply Flibe as a liquid blanket material, a heat transfer enhancement system is required because the Flibe is a high Prandtl number fluid. The purpose of this study is to visualize the detailed flow fields in the packed-bed tube, which is expected to be utilized for the heat transfer enhancement. The visualization inside the packed-bed tube from various angles is performed by using a PIV system with a refractive index matching technique. Pressure loss characteristics in the packed-bed tube whose sphere diameter is half the length of tube inside diameter are evaluated and it is found that a drag model could be suitable to estimate the pressure loss of the packed-bed tube.