An ultrasonic treatment apparatus comprising: an electric power source configured to output a vibration generating electric power; an ultrasonic transducer configured to generate an ultrasonic vibration by the vibration generating electric power from the electric power source; a treatment section which is configured to perform a treatment by use of the ultrasonic vibration generated in the ultrasonic transducer; a jaw that is openable and closable relative to the treatment section; an opening or closing operation input section to which an opening or closing operation to open or close the jaw is input; a movement unit (13; 62; 63) configured to open or close the jaw by movement in accordance with the opening or closing operation in the opening or closing operation input section; a movement detector which is configured to detect the movement of the movement unit (13; 62; 63); and an impedance detecting section which is configured to detect an ultrasonic impedance value of the ultrasonic transducer, characterized by a peak judging section which is configured to detect a peak of the ultrasonic impedance value on the basis of detection results of changes with time of the ultrasonic impedance value; and a control section which is configured to control the peak judging section to a detection disallowed state where a detection of the peak of the ultrasonic impedance value is not executed when the movement unit (13; 62; 63) is not placed within a prescribed range based on a detection result of the movement of the movement unit (13; 62; 63) in the movement detector, and which is configured to perform, when the peak of the ultrasonic impedance value is detected by the peak judging section, one of stopping or decreasing an output of the vibration generating electric power, and notifying that the peak of the ultrasonic impedance value has been detected. an electric power source configured to output a vibration generating electric power; an ultrasonic transducer configured to generate an ultrasonic vibration by the vibration generating electric power from the electric power source; a treatment section which is configured to perform a treatment by use of the ultrasonic vibration generated in the ultrasonic transducer; a jaw that is openable and closable relative to the treatment section; an opening or closing operation input section to which an opening or closing operation to open or close the jaw is input; a movement unit (13; 62; 63) configured to open or close the jaw by movement in accordance with the opening or closing operation in the opening or closing operation input section; a movement detector which is configured to detect the movement of the movement unit (13; 62; 63); and an impedance detecting section which is configured to detect an ultrasonic impedance value of the ultrasonic transducer, characterized by a peak judging section which is configured to detect a peak of the ultrasonic impedance value on the basis of detection results of changes with time of the ultrasonic impedance value; and a control section which is configured to control the peak judging section to a detection disallowed state where a detection of the peak of the ultrasonic impedance value is not executed when the movement unit (13; 62; 63) is not placed within a prescribed range based on a detection result of the movement of the movement unit (13; 62; 63) in the movement detector, and which is configured to perform, when the peak of the ultrasonic impedance value is detected by the peak judging section, one of stopping or decreasing an output of the vibration generating electric power, and notifying that the peak of the ultrasonic impedance value has been detected.