An ultrasound diagnostic apparatus comprises a transducer array for transmitting ultrasonic beams to a subject, a multiplexer for sequentially selecting one channel of reception signal in every N number of channels of reception signals out of a plurality of channels of reception signals outputted from the transducer array which has received receiving ultrasonic echoes from the subject, a plurality of reception signal processors for sequentially processing an N number of channels of reception signals selected by the multiplexer to produce reception data, a beam former for performing beam forming on reception data sequentially produced by the plurality of reception signal processors and having time difference to produce sound ray signals, and an image producing unit for producing an ultrasound image based on the sound ray signals produced by the beam former.