An ultrasound diagnostic device including: a transmitter which outputs a driving signal for a C-mode image to an ultrasound probe sending and receiving ultrasound; a receiver which obtains a reception signal from the ultrasound probe; and a controller which: calculates an inner product value of packet data of the reception signal and a first orthonormal basis for each degree; sets a conversion function to convert the inner product value into a removal rate to remove a clutter component; converts the calculated inner product value into the removal rate for each degree by using the set conversion function; and generates image data from which a signal component of the C-mode image is removed according to the removal rate for each degree.