Quantitative indices for declined red blood cell functions are required to avoid an inappropriate extracorporeal circulation. Optical methods without chemical treatment attract attention. Although several authors reported the relationship between scattering properties and changes in red blood cell morphology such as acanthocytosis observed in the early stage of functional decline, there are various issues in practical application such as expensive instruments and spectral contamination of the scattering property by hemoglobin absorption. In the present study, we used Monte Carlo simulation to examine the feasibility of evaluating scattering anisotropy of red blood cells in an original thin cuvette that we designed using combinations of cover glasses. First, we modeled the geometry of a goniometer using HeNe laser at 633 nm, detectors, and the original thin cuvette containing intralipid as scatterers with known optical properties. Next, angular conditions appropriate to the evaluation method were examined. The scattered intensity of the simulation in the range of 6 to 60 deg was in good agreement with Henyey-Greenstein function representing single scattering. Based on the simulation, we fabricated a prototype goniometer. The prototype was validated by measuring light scattering of intralipid as sample and comparing the results with those obtained from the simulation. The scattering anisotropy g obtained by fitting the Henyey-Greenstein function was 0.705, and was close to 0.74 set in the simulation. The scattering anisotropy of 1% intralipid measured by the prototype was 0.731. Finally, we measured angular dependence of light scattering in red blood cells. The measured scattering anisotropy of isotonic red blood cells with 5% hematocrit was 0.961, and was almost consistent with the values reported in the literature. The goniometer proposed in this study may be a quantitative tool that can be used as an alternative to blood smear examination.