An ultrasound diagnostic apparatus having a continuous wave Doppler mode. A line switching section is provided between an array transducer and a unit which has a CW transmission section and a CW reception section, for changing a transmitting and receiving aperture pattern. When a first transmitting and receiving aperture pattern is set on the array transducer, a first aperture functions as a transmitting aperture and a second aperture functions as a receiving aperture. When a second transmitting and receiving aperture pattern is set on the array transducer, the second aperture functions as a transmitting aperture and a first aperture functions as a receiving aperture. The patterns are switched whenever predetermined amount of time has elapsed after a prescribed event such as a pattern change, resumption of continuous wave reception, and so on. As such, localized heat generation or deterioration on the array transducer can be prevented.