Cellulose, gum, and polysaccharides are the typical example of the biological polyelectrolytes. Rheology of polyelectrolyte solutions has received significant attention owing to their pragmatic utility for solution characterization and processing. The Rouse-Zimm model based on the polymer dynamics theory allows us to predict the relaxation time of polyelectrolyte dilute solution as a function of the intrinsic viscosity. In finite concentrated solutions, the empirical analysis adopted in this study is quite useful to examine the relaxation behavior, considering that proper theories are not well-clarified and experimental measurements are rather complicated. For the xanthan gum selected as the biological polyelectrolyte model of a semiflexible chain, we measured rheological properties of shear viscosity and first normal stress difference in dilute and semidilute solutions over a wide range of shear rates. Power-law scaling relations are commonly observed in the region of the shear rate above 1.0 1/s. Accurate regressions on shear viscosity and normal stress difference present empirical plots as functions of the shear rate and the solution concentration, from which each of relevant fitting parameters are determined. Empirically determined curves agree well with the experimental data, ensuring that the empirical formula for the characteristic relaxation time is applicable up to finite concentrations, which has been rarely reported in the literature. In addition, we interpreted the non-Newtonian fluid behavior over a full range of shear rates by applying the constitutive model based on the Carreau A type.