Ultrasonic treatment tool

An ultrasonic treatment tool comprising:

• a tubular portion configured to be inserted into a subject;
• an ultrasonic treatment unit provided on a distal end side of the tubular portion, the ultrasonic treatment unit including
• an ultrasonic transducer configured to generate ultrasonic vibration, and
• an ultrasonic blade that is connected to a distal end portion of the ultrasonic transducer and that includes a treatment portion configured to apply the ultrasonic vibration generated by the ultrasonic transducer to a biological tissue to treat the biological tissue;
• and
• a support configured to
• accommodate the ultrasonic treatment unit inside the support with the treatment portion protruding from an inside toward an outside of the support, and
• support the ultrasonic treatment unit at a first node position of vibration of the ultrasonic transducer and at a second node position of vibration of the ultrasonic blade in the support when each of the ultrasonic transducer and the ultrasonic blade vibrates at a predetermined resonance frequency.