In this study, a simple kneading machine with a visualization window was prepared to experimentally analyze the behavior of the full filled viscoelastic fluid stirred by a single rotor. Several different types of viscoelastic non-Newtonian fluid were tested and particle image velocimetry (PIV) was used to quantitatively investigate the velocity distribution in the chamber. The obtained results showed that overall flow structure was dominated by the degree of non-Newtonian property. It was also shown that different flow patterns behind the trailing edge of the rotor tip depended on the degree of viscoelasticity.