According to one embodiment, an ultrasound diagnostic apparatus comprises processing circuitry. The processing circuitry sets one of wavelengths of a plurality of light sources as a reference wavelength, normalize an intensity of light having a wavelength other than the reference wavelength, which is detected by a pair of each light irradiation unit and each optical detector, with an intensity of light having the reference wavelength, calculate a first value for each pair by nonlinear enhancement correction of a normalized light intensity, calculate a second value for the each pair by nonlinear reduction correction of an intensity of light having the reference wavelength detected by the each pair, and calculate an evaluation value based on a value obtained by multiplication of the first value and the second value for the each pair.
