A medical apparatus that comprises: a vibration transmission member that has a tip part, a base part that is provided on a transducer side, and an intermediate part that is provided between the tip part and the base part a first cross-sectional area reduction part that is provided to the tip part and that makes the cross-sectional area of the tip part with respect to a plane that intersects the center axis of the vibration transmission member smaller than the cross-sectional area of the intermediate part with respect to a plane that intersects the center axis and a second cross-sectional area reduction part that is where the tip-most node of ultrasonic vibrations is positioned when the vibration transmission member is resonating, that is provided, with respect to the center axis, on the opposite side from the first cross-sectional area reduction part, and that makes the cross-sectional area, with respect to a plane that intersects the center axis, of the half of the vibration transmission member that is on the opposite side from the first cross-sectional area reduction part smaller than the cross-sectional area, with respect to a plane that intersects the center axis, of the half of the vibration transmission member that is on the first cross-sectional area reduction part side.La présente invention concerne un appareil médical qui comprend : un élément de transmission de vibrations qui comporte une partie de pointe, une partie de base qui est disposée sur un côté de transducteur, et une partie intermédiaire qui est disposée entre la partie de pointe et la partie de base une première partie de réduction daire de section transversale qui est disposée sur la partie de pointe et qui rend laire de section transversale de la partie de pointe par rapport à un plan qui coupe laxe central de lélément de transmission de vibration, plus petite que laire de section transversale de la partie intermédiaire par rapport à un plan qui coupe laxe central et une deuxième partie de réd
