An ultrasound observation apparatus for generating an ultrasound image based on an ultrasound signal acquired by an ultrasound probe, the ultrasound probe having an ultrasound transducer configured to transmit ultrasound to an observation target and receive the ultrasound reflected from the observation target, the ultrasound observation apparatus comprising: a frequency analysis unit configured to analyze a frequency of the ultrasound signal to calculate a plurality of frequency spectra in accordance with reception depths and receiving directions of the ultrasound signal; a feature calculation unit configured to calculate features of the plurality of frequency spectra; an attenuation factor setting unit configured to use an attenuation factor candidate value per unit length and per unit frequency to perform attenuation correction on the features of the frequency spectra for removing an influence of the ultrasound; and a feature correction unit configured to calculate a cumulative attenuation factor per unit frequency at a sampling point, and to perform attenuation correction on the features using the cumulative attenuation factor to calculate a corrected feature, characterized in that the attenuation factor setting unit is configured to use each of a plurality of attenuation factor candidate values per unit length and per unit frequency that give different attenuation characteristics when the ultrasound propagates through the observation target, in each of divided regions obtained by dividing the ultrasound image into a plurality of regions, to perform the attenuation correction on the features of the frequency spectra for removing an influence of the ultrasound, thereby to calculate a preliminarily corrected feature of each of the frequency spectra for each of the attenuation factor candidate values, and to set an optimum attenuation factor for the observation target among the plurality of attenuation factor candidate values based on the calculated preliminarily corrected feature; and the feature correction unit is configured to calculate the cumulative attenuation factor per unit frequency at the sampling point, using an optimum attenuation factor of a divided region present between a surface of the ultrasound transducer and the sampling point among optimum attenuation factors set respectively for the divided regions by the attenuation factor setting unit. a frequency analysis unit configured to analyze a frequency of the ultrasound signal to calculate a plurality of frequency spectra in accordance with reception depths and receiving directions of the ultrasound signal; a feature calculation unit configured to calculate features of the plurality of frequency spectra; an attenuation factor setting unit configured to use an attenuation factor candidate value per unit length and per unit frequency to perform attenuation correction on the features of the frequency spectra for removing an influence of the ultrasound; and a feature correction unit configured to calculate a cumulative attenuation factor per unit frequency at a sampling point, and to perform attenuation correction on the features using the cumulative attenuation factor to calculate a corrected feature, characterized in that the attenuation factor setting unit is configured to use each of a plurality of attenuation factor candidate values per unit length and per unit frequency that give different attenuation characteristics when the ultrasound propagates through the observation target, in each of divided regions obtained by dividing the ultrasound image into a plurality of regions, to perform the attenuation correction on the features of the frequency spectra for removing an influence of the ultrasound, thereby to calculate a preliminarily corrected feature of each of the frequency spectra for each of the attenuation factor candidate values, and to set an optimum attenuation factor for the observation target among the plurality of attenuation factor candidate values based on the calculated preliminarily corrected feature; and the feature correction unit is configured to calculate the cumulative attenuation factor per unit frequency at the sampling point, using an optimum attenuation factor of a divided region present between a surface of the ultrasound transducer and the sampling point among optimum attenuation factors set respectively for the divided regions by the attenuation factor setting unit.