An ultrasonic treatment device comprises a connecting unit. The connecting unit including a first engagement portion which engages with a first screw portion and a second engagement portion which engages with a second screw portion, the connecting unit connecting a probe and a vibration generating unit to transmit the ultrasonic vibrations to the probe by rotation relative to the vibration generating unit and a treatment unit in a first direction around a longitudinal axis, and disconnecting the probe and the vibration generating unit from each other by rotation in a second direction opposite to the first direction.
