Provided is an ultrasound diagnostic and treatment device for tumors which is used in combination with a phase-shift ultrasound contrast agent. By using a phase-shift ultrasound contrast agent, irradiating phase-shift ultrasonic waves from a phase-shift ultrasonic wave transmitter (18), irradiating ultrasonic waves for holding microbubbles from an ultrasonic wave transmitter (29) for holding microbubbles, and using a phase-shift detecting ultrasonic wave transceiver (19) to observe the phase shift, the ultrasound diagnostic and treatment device generates and holds the microbubbles in advance on the entire site (16) requiring treatment, and irradiates ultrasonic waves for treatment having a moderate intensity of 1 kW/cm2 or lower on the entire site (16) requiring treatment with the microbubbles as the target from a ultrasonic wave transmitter (20) for treatment.