Abstract: An ultrasonic apparatus for thereapeutical use, especially for remedying a malignant tumor, through activation of a drug at a desired local portion inside of a living body by sequentially irradiating a plurality kinds of convergent ultrasonic waves having different focal positions of different acoustic pressure distribution shapes but having a mutually overlapping focal zone and by switching them within a short period. The drug is activated as a promotor for an ultrasonic therapeutical effect through continuous generation and rupture of cavitation caused by the irradiated and switched ultrasonic waves.