An ultrasound observation apparatus includes: a frequency analysis unit that analyzes a frequency of the ultrasound signal to calculate frequency spectra according to a reception depth and a reception direction of the ultrasound signal; an optimal attenuation rate setting unit configured to: calculate features of the frequency spectra; perform attenuation correction on the features of the frequency spectra for eliminating influence of attenuation of the ultrasound wave, using attenuation rate candidate values providing different attenuation characteristics which are attenuation characteristics in propagating the ultrasound wave through the observation target, thereby to calculate corrected features of the frequency spectra for each of the attenuation rate candidate values; and set an optimal attenuation rate to the observation target from among the attenuation rate candidate values, based on the corrected features; and an attenuation rate image data generation unit that generates attenuation rate image data for displaying information on the optimal attenuation rate.