Ultrasonic treatment apparatus

An ultrasonic treatment apparatus comprising:

• an electric power source which is configured to output vibration generating electric power;
• a vibration generating section which is configured to generate an ultrasonic vibration by supplying the vibration generating electric power from the electric power source;
• a treatment section to which the ultrasonic vibration generated in the vibration generating section is transmitted, and which is configured to perform a treatment by use of the transmitted ultrasonic vibration;
• a jaw which is openable and closable relative to the treatment section, and which includes a contact portion contactable with the treatment section in a state where the jaw is closed relative to the treatment section;
• an impedance detecting section which is configured to detect an ultrasonic impedance value of the vibration generating electric power with time, in a state where the vibration generating electric power is output from the electric power source;
• a gradual decrease detecting section which is configured to detect a gradual decrease start point to start gradual decrease of the ultrasonic impedance value on the basis of a detection result in the impedance detecting section;
• a tentative peak value holding section which is configured to hold the ultrasonic impedance value at the detected gradual decrease start point as a tentative peak value;
• and
• a peak judging section which is configured to judges whether the held tentative peak value is a target peak of a detection target by comparing, relative to the held tentative peak value, changes with time of the ultrasonic impedance value after the gradual decrease start point.