An ultrasound observation apparatus is configured to: calculate frequency spectra based on an ultrasound echo, the ultrasound echo being obtained by irradiating an observation target with an ultrasound wave and receiving the ultrasound wave reflected from the observation target； calculate features of the frequency spectra； perform an attenuation correction on each of the features of the frequency spectra using each of at least three attenuation rate candidate values giving different attenuation characteristics in propagating the ultrasound wave through the observation target, thereby calculating corrected features of the frequency spectra； calculate a statistical dispersion of the corrected features for each attenuation rate candidate value； generate a quadratic function based on the statistical dispersion； set one of the attenuation rate candidate values which gives a minimum statistical dispersion in the quadratic function, as an optimal attenuation rate； and generate feature image data based on the corrected features using the optimal attenuation rate.
