An ultrasonic surgical instrument comprises an ultrasonic transducer producing ultrasonic vibration, a transmission member transmitted ultrasonic vibration from the proximal end to the distal end, a sheath in which the transmission member is inserted, a procedural unit provided to the distal end of the transmission member so that it projects from the distal end of the sheath, and treating a surgical target portion using ultrasonic vibration, a procedural unit main body provided in the procedural unit, a procedural member provided in the sheath so that it projects from the distal end of the sheath to treat the surgical target portion, and a procedural member main body provided at the distal end of the procedural member. In the ultrasonic surgical instrument, the procedural member main body overlaps with the procedural unit main body, and thereby, the procedural member main body and the procedural unit main body treat the portion.