The present invention displays an ultrasound image while making the positional relationship with an ultrasound probe clear. The ultrasound diagnostic device (10) is provided with: an ultrasound probe (2); a first position detecting means (4, 5) for detecting the position of the ultrasound probe (2); an ultrasound image generating means (6) for generating an ultrasound image using a reflective echo signal; an ultrasound volume data generating means (9) for generating three dimensional ultrasound volume data by superimposing ultrasound images; a reference image generating means (12) for generating an ultrasound reference image of any cross-sectional area using the ultrasound volume data and displaying in a superimposed manner an ultrasound probe mark which indicates the position of the ultrasound probe in a position corresponding to the position of the ultrasound probe detected by the first position detection means in the ultrasound reference image; and a displaying means (15) for displaying the ultrasound image and the ultrasound reference image.