An ultrasound observation device is configured to generate, based on ultrasound signals acquired by an ultrasound transducer performing transmission and reception to and from an observation target, plural ultrasound images along time series. The ultrasound observation device includes: a movement amount calculating circuit configured to calculate, from the plural ultrasound images, an amount of movement that is an amount moved by a subject captured in an ultrasound image of the latest frame relatively to the subject captured in an ultrasound image of a past frame； a reliability determining circuit configured to determine a reliability of the amount of movement calculated by the movement amount calculating circuit； and a frozen image selecting circuit configured to select a frozen image from the plural ultrasound images, based on the amount of movement and the reliability, when input of a freeze instruction signal has been received.
