A vibration transmission member for an ultrasonic treatment tool includes: a main body including a central axis, a distal end (DE), and a proximal end (PE), a center moving portion (CMP) at a distal side of a node where the DE meets the CMP, the node being at a most DE of the main body, and a curved portion (CP) at a distal side of the CMP. In a direction from a PE of the CP toward a DE of the CP, the CP is curved in a first direction. The center of gravity of the CMP moves along the CMP toward the DE of the CMP, the center of gravity moves relative to the central axis in a second direction. The CP extends from the DE of the main body to the PE of the CP. The CP includes a plurality of notches along a periphery of the CP.