The ultrasonic probe has a block shaped treatment section for cutting an object to be treated by ultrasonic vibration.Department of treatmentA first plane of tip along the longitudinal axisIt is provided on the proximal end side along the longitudinal axis than the first planeHaving a first step between the first surface and the first surfaceHaving a second plane orthogonal to or perpendicular to the longitudinal axisWhen viewed from the leading end to the proximal end along the longitudinal axisAmong the first facesThe dimension along the first orthogonal direction perpendicular to the longitudinal axis isOf the second planeIt has a portion smaller than the dimension along the first orthogonal direction.超音波プローブは、超音波振動により処置対象を切削するブロック状の処置部を有する。処置部は、前記長手軸に沿って先端の第１の面と、前記第１の面よりも前記長手軸に沿って基端側に設けられ、前記第１の面との間に第１の段差を有し、前記長手軸に対して直交又は略直交する第２の面とを有し、前記長手軸に沿って先端側から基端側を見たとき、前記第１の面のうち、前記長手軸に対して直交する第１の直交方向に沿う寸法が、前記第２の面のうち、前記第１の直交方向に沿う寸法よりも小さい部分を有する。
