A treatment device includes: a probe including a treatment portion that performs treatment to a treatment target portion by transmission of ultrasonic vibration； a first sheath having a first edge and enclosing a periphery of the probe； a second sheath having a second edge and enclosing a periphery of the first sheath； a suction path including a suction opening between the first edge and the second edge and provided between the first sheath and the second sheath； and a connection part communicating with the suction path and connected to a suction source.
