An ultrasonic surgical instrument for boring a hole in a femur, including: an ultrasonic vibrator capable of generating ultrasonic vibration； a probe including a proximal end portion connected with the ultrasonic vibrator and a distal end treatment portion capable of boring a bone hole in the femur, and transmitting the ultrasonic vibration； and a cylindrical member covering the proximal end portion of the probe and not covering an exposed portion including the distal end treatment portion. The distal end treatment portion includes a columnar portion having a cross-sectional area that is larger than that of a remainder of the exposed portion of the probe.
