This ultrasonic diagnostic device transmits an ultrasonic beam to a subject from an array transducer in which a plurality of first elements are arranged, and receives an ultrasonic echo from the subject to perform ultrasonic diagnosis. The ultrasonic diagnostic device is provided with: an element data memory (7) which stores a plurality of element data which are output from the plurality of first elements that received an ultrasonic echo reflected by a reflection point in the subject as a result of transmission of an ultrasonic beam to the reflection point a time difference calculation unit (21) which calculates a plurality of time differences between element data corresponding to a reference element which is one of the plurality of first elements and a plurality of element data corresponding to a plurality of measurement elements which are elements other than the reference element of the plurality of first elements a sound velocity calculation unit (22) which calculates a plurality of individual sound velocities corresponding to the plurality of measurement elements on the basis of the distance from the reflection point to the reference element, the distances from the reflection point to the plurality of measurement elements, and the plurality of time differences calculated by the time difference calculation unit (21) and an overall sound velocity determination unit (23) which determines the overall sound velocity on the basis of the individual sound velocities calculated by the sound velocity calculation unit (22).La présente invention concerne un dispositif de diagnostic ultrasonore qui transmet un faisceau ultrasonore à un sujet depuis un transducteur de réseau dans lequel une pluralité de premiers éléments sont agencés, et reçoit un écho ultrasonore depuis le sujet pour effectuer un diagnostic ultrasonore. Le dispositif de diagnostic ultrasonore est pourvu de : une mémoire de données délément (7) qui stocke une pluralité de données délément qui sont délivrées e
