An ultrasonic probe to transmit ultrasonic vibration along a longitudinal axis from the proximal end toward the distal end thereof, includes: a first area including a proximal end portion, a distal end portion and a center axis which is defined by the proximal end portion and the distal end portion and which is parallel to the longitudinal axis, the first area having an antinode position of the ultrasonic vibration at the distal end portion； a treatment section located on a distal end side with respect to the distal end portion of the first area and having a center of gravity at a position displaced from the center axis of the first area； and a second area located between the distal end portion of the first area and the treatment section so as to be continuous with the distal end portion of the first area and configured to have a gravity center axis positioned parallel to the center axis of the first area so as to pass through the center of gravity of the treatment section or be closer to the center of gravity than the center axis, wherein the gravity center axis of the second area is displaced from the center axis of the first area at the distal end portion of the first area.
