PURPOSE: To prevent the puncture of a pipe cavity wall due to laser beam, to perform the endoscopic observation of a pipe cavity and to also easily perform the flashing of a physiological saline solution, by mounting a spacing chip holding a probe main body in a non-contact state with respect to the inner wall surface of the pipe cavity to the leading end part of the probe main body and forming a space part to a part of said chip.

CONSTITUTION: A probe main body 1 is inserted in a blood vessel 18 through the channel of an endoscope 17 and laser beam is allowed to irradiate a thrombus part 19 from a ceramic chip 7 to cauterize and remove he same. At this time, since the probe main body 1 is stably held at the approx. center of the blood vessel 18 by am spacing chip 9, the puncture of the blood vessel due to laser beam can be prevented. Since a circular arc-shaped notch part 11 is provided to the spacing chip 9, the interior of the blood vessel 18 beyond the spacing chip 9 can be observed by the endoscope 17. Therefore, the thrombus part 19 can be treated while the irradiation position with laser beam is confirmed by the endoscope 17. Further, since the blood vessel 18 is not closed by the spacing chip 9, the flashing of a physiological saline solution can be easily performed.