An ultrasound observation apparatus to which an ultrasound probe is connectable, the ultrasound probe including a capacitive micromachined ultrasound transducer whose sensitivity can be controlled according to an applied bias voltage, the ultrasound observation apparatus including a transmit section that outputs a transmit signal for causing ultrasound to be transmitted a receive section that performs signal processing on a received receive signal a bias voltage outputting section that varies the applied bias voltage, an image mode setting section that designates and sets an image mode for displaying an ultrasound image corresponding to ultrasound scanning a parameter setting section that designates and sets a parameter for signal processing performed by the transmit section or the receive section, and a control section that controls the bias voltage based on a designation signal corresponding to the designation and setting of the image mode and the parameter.
