An ultrasound observation device is configured to acquire an ultrasound signal obtained by converting ultrasound received by an ultrasound transducer to an electric signal, the ultrasound transducer transmitting the ultrasound to an observation target and receiving ultrasound reflected from the observation target. The ultrasound observation device includes: a processor configured to perform predetermined computation on the ultrasonic signal. The processor is configured to: analyze a frequency of a signal generated based on the ultrasound signal to calculate a plurality of frequency spectra compare a physical quantity based on the ultrasound reflected from the observation target with a threshold set according to the physical quantity and calculate a frequency feature based on a frequency spectrum calculated by the analyzing and a comparison result obtained by the comparing.
