Ceramic fibers that use as heat insulating materials for high-temperature furnace are produced in the process that a high-speed jet blows molten ceramic dropping from a furnace. The insulation performance is improved with longer length of the fibers and with lower content of spherical shots that solidifies without fiberization. These fiber properties are strongly affected by the shape of the jet nozzle though there does not exist the logical design method for it. Empirical methods are limited to optimize it. So that to detail information about the fiberization process is needed. In this study, visualization of the process using high shutter speed camera and schlieren method are attempted. The results from the high speed shutter camera show that fiberization process is completed before the fibers are blown downstream of the nozzle diameter.Visualization of schlieren method suggests existence of strong turbulence right downstream the nozzle which may affects the fiberization.