To provide an energy accessory capable of adjusting an coagulating capability and an incising capability, and improving an operation efficiency. An energy accessory (24) includes an ultrasonic vibrator configured to generate ultrasonic vibration, an elongated probe (32) whose proximal end is connected to the ultrasonic vibrator and configured to transmit the ultrasonic vibration generated by the ultrasonic vibrator from a proximal end side to a distal end side to apply the ultrasonic vibration to living tissue, a sheath (50) provided on the proximal end side of the probe (32), a grasping portion (65) provided on a distal end portion of the sheath (50) and configured to be rotated with respect to the probe (32) and brought into contact with the living tissue disposed on the side of the probe (32), whereby the living tissue is grasped in cooperation with the probe, and a treatment mode variable mechanism (66, 68) configured to change a treatment mode of a treatment with respect to the living tissue brought into contact with the grasping portion (65).
