In an ultrasonic probe a tapered section in which a sectional area perpendicular to a longitudinal axis decreases from a proximal side toward a distal side is provided on the distal side with respect to a probe main body section. When the probe main body section and the tapered section vibrate in an established frequency range, a most distal vibration node positioned most distally among vibration nodes is positioned on the proximal side with respect to a proximal end of the tapered section, and a ⅛ wavelength of the vibration is smaller than a taper dimension from the proximal end the tapered section to a distal end of the tapered section in a longitudinal axis direction.