A treatment device is constituted of: an ultrasonic vibration element unit; a probe unit that can be attached or detached by rotating the ultrasonic vibration element unit, transmits ultrasonic vibration generated by the ultrasonic vibration element unit to a distal end side, and gives a treatment; a handle unit that has the probe unit penetrating therethrough and is configured to hold the probe unit so that its distal end extends; and a protruding portion provided to prevent the probe unit and the handle unit from relatively revolving around an axis of the probe, the handle unit including the probe unit that transmits the ultrasonic vibration and being attachable to/detachable from the ultrasonic vibration element unit.