Disclosed is a method and apparatus of generating a temperature image during ultrasonic treatment, the method including setting a first plane indicating a heating region where ultrasonic waves for treatment are irradiated and setting a second plane indicating a protective region around the heating region; irradiating the first plane with ultrasonic waves for diagnosis at a first frame rate, and irradiating the second plane with the ultrasonic waves for diagnosis at a second frame rate, the second frame rate being lower than the first frame rate; and generating the temperature image using frame images acquired from irradiating the ultrasonic waves for diagnosis.