A vibration transmission member configured to resonate upon transmission of ultrasonic vibration thereto from a transducer that is configured to generate the ultrasonic vibration, the vibration transmission member comprising: a distal end portion; a proximal end portion provided closer to the transducer; an intermediate portion provided between the distal end portion and the proximal end portion; an inclined portion, which is provided to the distal end portion, and is inclined with respect to a central axis of the vibration transmission member in a state that the inclined portion is closer to the central axis as the inclined portion is closer to a distal end of the distal end portion, and a first cross-sectional area reduction portion, which makes a cross-sectional area of the distal end portion concerning a plane intersecting with the central axis of the vibration transmission member smaller than a cross-sectional area of the intermediate portion concerning a plane intersecting with the central axis by the inclined portion, whereby the vibration transmission member further includes: a second cross-sectional area reduction portion which is formed in the proximal end portion so that an abnormal vibration due to the first cross-sectional area reduction portion formed in the distal end portion is set off by an abnormal vibration due to the second cross-sectional area reduction portion, at which a node position of the ultrasonic vibration nearest to the distal end portion is located while the vibration transmission member is resonating, and which is provided opposite to the first cross-sectional area reduction portion with respect to the central axis, the second cross-sectional area reduction portion making a cross-sectional area concerning a plane intersecting with the central axis of a half portion of the vibration transmission member located opposite to the first cross-sectional area reduction portion smaller than a cross-sectional area concerning a plane intersecting with the central axis of a half portion of the vibration transmission member located closer to the first cross-sectional area reduction portion, the second cross-sectional area reduction portion having a shape different from that of the first cross-sectional area reduction portion and asymmetrical to that of the first cross-sectional area reduction portion with respect to the central axis. a distal end portion; a proximal end portion provided closer to the transducer; an intermediate portion provided between the distal end portion and the proximal end portion; an inclined portion, which is provided to the distal end portion, and is inclined with respect to a central axis of the vibration transmission member in a state that the inclined portion is closer to the central axis as the inclined portion is closer to a distal end of the distal end portion, and a first cross-sectional area reduction portion, which makes a cross-sectional area of the distal end portion concerning a plane intersecting with the central axis of the vibration transmission member smaller than a cross-sectional area of the intermediate portion concerning a plane intersecting with the central axis by the inclined portion, whereby the vibration transmission member further includes: a second cross-sectional area reduction portion which is formed in the proximal end portion so that an abnormal vibration due to the first cross-sectional area reduction portion formed in the distal end portion is set off by an abnormal vibration due to the second cross-sectional area reduction portion, at which a node position of the ultrasonic vibration nearest to the distal end portion is located while the vibration transmission member is resonating, and which is provided opposite to the first cross-sectional area reduction portion with respect to the central axis, the second cross-sectional area reduction portion making a cross-sectional area concerning a plane intersecting with the central axis of a half portion of the vibration transmission member located opposite to the first cross-sectional area reduction portion smaller than a cross-sectional area concerning a plane intersecting with the central axis of a half portion of the vibration transmission member located closer to the first cross-sectional area reduction portion, the second cross-sectional area reduction portion having a shape different from that of the first cross-sectional area reduction portion and asymmetrical to that of the first cross-sectional area reduction portion with respect to the central axis.