Vibrating body unit and ultrasonic probe

An ultrasonic probe which is separably connected to a vibration generating unit including a vibration generator, the vibration generator being configured to generate ultrasonic vibration, amplitude of the generated ultrasonic vibration at the vibration generator having a predetermined correlation with a frequency, the predetermined correlation being positive when the amplitude increases with an increase in frequency, or negative when the amplitude decreases with the increase in frequency, the ultrasonic probe comprising:

• a vibration transmitting member which has a proximal end and a distal end, and which is configured to transmit, to a distal side, the ultrasonic vibration transmitted from the vibration generating unit to the proximal end in a longitudinal axis direction;
• and
• an amplitude enlarger which is provided in the vibration transmitting member, and which is configured to enlarge the amplitude of the ultrasonic vibration at an amplitude enlargement rate in a direction of transmission of the ultrasonic vibration, the amplitude enlargement rate being a ratio of:
• an output amplitude at a first position on a distal side of the amplitude enlarger, and
• an input amplitude at a second position on a proximal side of the amplitude enlarger,
• wherein:
• a correlation between the amplitude enlargement rate and the frequency is:
• (i) positive when the amplitude enlargement rate increases with the increase in frequency, or
• (ii) negative when the amplitude enlargement rate decreases with the increase in frequency, and
• the correlation between the amplitude enlargement rate of the amplitude enlarger and the frequency is opposite to the predetermined correlation between the generated ultrasonic vibration at the vibration generator and the frequency.