Providing a blood vessel function inspecting apparatus capable of calculating a blood shear stress concurrently with measurement of a change ratio of a diameter of a blood vessel after releasing of the blood vessel from blood flow obstruction, while reducing a load of arithmetic operation for the calculation of the blood shear stress. Viscosity-shear rate calculating means 104 calculates a viscosity-shear rate relationship VCSR between blood viscosity µ and blood shear rate SR, before the blood vessel releasing, on the basis of a rest-time blood flow velocity distribution DS RT measured at rest, and blood shear stress calculating means 112 measures a blood velocity within the blood vessel 20 concurrently with the measurement of the change ratio R of the diameter of the blood vessel 20 after the blood vessel releasing, and calculates a blood shear stress SS on the basis of the measured blood flow velocity SPD and according to the above-described viscosity-shear rate relationship VCSR. Accordingly, the blood shear stress SS can be calculated in a real-time processing fashion with a low load of arithmetic operation, concurrently with the measurement of the change ratio R of the diameter of the blood vessel 20 after the blood vessel releasing, without measurements after the blood vessel releasing, which would cause a high load of arithmetic operation, such as a measurement according to the Navier-Stokes equations.
