An ultrasound observation system (1) is provided that includes: an ultrasound transducer (11) that transmits ultrasound to a subject and receives ultrasound from the subject and generates an ultrasound signal； a first automatic pressurization mechanism (12) that applies a pressing force to the subject to generate a pressurization displacement； a displacement measurement circuit for elasticity image generation (28) that measures a displacement amount for an image of the subject based on the ultrasound signal； an elasticity modulus calculation circuit (29) that calculates an elasticity modulus of the subject based on the displacement amount for an image； a signal waveform analysis circuit (31) that analyzes a waveform of a signal that is based on a displacement of the subject and acquires a local maximum point of the displacement and a displacement cycle； and a pressurization mechanism control circuit (32) that, based on the signal waveform analysis result, causes the first automatic pressurization mechanism (12) to perform pressurization at the same timing as the local maximum point of the displacement in synchrony with the displacement cycle.
