An ultrasound diagnostic apparatus comprises: a detector for detecting a direction of radial expansion/contraction of a vascular wall associated with a heartbeat in a long-axis image of the vascular wall based on amplitude information of reception signals outputted from an ultrasound probe when a first ultrasonic beam is transmitted and received to and from a blood vessel of a subject through the ultrasound probe by a transmitter/receiver a controller for controlling the transmitter/receiver so as to transmit and receive a second ultrasonic beam parallel to the detected vascular wall expansion/contraction direction through the ultrasound probe a tracker for tracking a movement of the vascular wall using amplitude information and phase information of the reception signals outputted from the ultrasound probe when the second ultrasonic beam is transmitted and received and a calculator for calculating elastic characteristics of the vascular wall based on the tracked vascular wall movement.
