An ultrasound diagnostic apparatus (1, 1A, 1B) that has an ultrasound probe and is used to compression-test an observation target within a subject by pressing the ultrasound probe against a body surface of the subject, the ultrasound diagnostic apparatus (1, 1A, 1B) comprising: an image acquisition unit that performs transmission of an ultrasound beam from the ultrasound probe toward the subject and acquires ultrasound images (U1, U2, U3, U4) consecutively and sequentially; a display unit that displays the ultrasound image (U1, U2, U3, U4) acquired by the image acquisition unit; a reference image holding unit that holds the ultrasound image (U1, U2, U3, U4) acquired by the image acquisition unit as a reference image in a state where a position of the ultrasound probe is fixed in order to depict a tomographic plane (FP1, FP2) of the observation target on the display unit; a movement vector calculation unit that calculates a movement vector indicating an image movement change between two ultrasound images (U1, U2, U3, U4) that are consecutive for each predetermined number of frames among the ultrasound images (U1, U2, U3, U4) sequentially acquired by the image acquisition unit; a movement vector integration unit that integrates the movement vectors that are respectively calculated by the movement vector calculation unit in the ultrasound images (U1, U2, U3, U4) from the time when the reference image is held by the reference image holding unit until the current time; a deformed image generation unit that generates a deformed image (D1, D3) in which the ultrasound image (U1, U2, U3, U4) held as the reference image by the reference image holding unit is moved and changed until the current time on the basis of the movement change integrated by the movement vector integration unit; a tomographic plane determination unit that determines whether or not a tomographic plane (FP1, FP2) of the subject depicted from the reference image and a tomographic plane (FP1, FP2) of the subject depicted from the ultrasound image of the current frame are the same as each other by comparing the deformed image (D1, D3) generated by the deformed image generation unit with the ultrasound image of the current frame acquired by the image acquisition unit; and a determination result notification unit that notifies a user of a determination result caused by the tomographic plane determination unit. an image acquisition unit that performs transmission of an ultrasound beam from the ultrasound probe toward the subject and acquires ultrasound images (U1, U2, U3, U4) consecutively and sequentially; a display unit that displays the ultrasound image (U1, U2, U3, U4) acquired by the image acquisition unit; a reference image holding unit that holds the ultrasound image (U1, U2, U3, U4) acquired by the image acquisition unit as a reference image in a state where a position of the ultrasound probe is fixed in order to depict a tomographic plane (FP1, FP2) of the observation target on the display unit; a movement vector calculation unit that calculates a movement vector indicating an image movement change between two ultrasound images (U1, U2, U3, U4) that are consecutive for each predetermined number of frames among the ultrasound images (U1, U2, U3, U4) sequentially acquired by the image acquisition unit; a movement vector integration unit that integrates the movement vectors that are respectively calculated by the movement vector calculation unit in the ultrasound images (U1, U2, U3, U4) from the time when the reference image is held by the reference image holding unit until the current time; a deformed image generation unit that generates a deformed image (D1, D3) in which the ultrasound image (U1, U2, U3, U4) held as the reference image by the reference image holding unit is moved and changed until the current time on the basis of the movement change integrated by the movement vector integration unit; a tomographic plane determination unit that determines whether or not a tomographic plane (FP1, FP2) of the subject depicted from the reference image and a tomographic plane (FP1, FP2) of the subject depicted from the ultrasound image of the current frame are the same as each other by comparing the deformed image (D1, D3) generated by the deformed image generation unit with the ultrasound image of the current frame acquired by the image acquisition unit; and a determination result notification unit that notifies a user of a determination result caused by the tomographic plane determination unit.