The position of a metal marker 5 relative to an optical fiber 6 is fixed, and the metal marker 5 can be moved up close to a target site such as a thrombus. It is preferable that the position, in an optical fiber longitudinal direction, of a front-end face of the optical fiber 6 is coincident with the position, in an optical fiber longitudinal direction, of a front-end face of the metal marker 5. More specifically, since the distance between the target site and the front end of the optical fiber 6 is known by radiography, it becomes unnecessary to use a large quantity of contrast agent and irradiate a laser beam depending on skill and intuition, and therefore an effective laser beam irradiation becomes possible.