An ultrasonic treatment apparatus includes an impedance detecting section detecting an ultrasonic impedance value with time, and a gradual decrease detecting section detecting a gradual decrease start point to start gradual decrease of the ultrasonic impedance value. The ultrasonic treatment apparatus includes a tentative peak value holding section holding the ultrasonic impedance value at the detected gradual decrease start point as a tentative peak value, and a peak judging section judging whether the held tentative peak value is a target peak by comparing, relative to the held tentative peak value, changes with time of the ultrasonic impedance value after the gradual decrease start point.
