An ultrasonic probe includes a treatment portion that has a through-hole or concave portions. The through-hole extends from a first outer surface to a second outer surface facing in an opposite direction to that of the first outer surface. The concave portions include a first concave portion on the first outer surface, and a second concave portion on the second outer surface. The treatment portion includes a blade formed along an edge of an opening of the through-hole or the first concave portion. An outer relay surface extends from the blade to the second outer surface and faces away from a center axis of the through-hole or the concave portions. A distance from the center axis to the blade is greater than or equal to a distance from the center axis to the outer relay surface at a position between the blade and the second outer surface.