It has been reported that the wall shear stress affects the biochemical function of endothelial cell and the development of arteriosclerosis plaque. Therefore, the quantitative estimation of the wall shear stress has possibilities to be useful for the prevention of arteriosclerosis. In this paper, a novel method for the real-time and quantitative estimation of intravascular shear stress distribution is proposed based on the estimates of the viscosity and the shear rate distribution. Experimental investigation, in which two types of fluids with different viscosity coefficient (water, and water mixed by PVA) flowed at a constant flow rate in a silicone tube with a simulated arteriosclerosis plaque, was performed. After estimating the viscosity coefficient and the shear rate distribution based on the ultrasonic measurements of the velocity vector distribution in the tube, the shear stress distributions were obtained. The averaged value of the shear stress distribution estimated in the higher viscosity fluid (water mixed by PVA: 0.3 Pa) became larger than that in the lower viscosity fluid (water: 0.1 Pa). These results reveal that the proposed method is technically valid for the quantitative shear stress estimation.