A laser beam guiding fiber comprising, in a tip portion of an optical fiber, an oscillating member which oscillates the tip of the optical fiber along a direction which intersects an axis of the optical fiber can irradiate a wide range with laser beam, since the tip of the optical fiber oscillates by means of the oscillating member along the direction which intersects the axis of the optical fiber and the irradiated position with the laser beam reciprocates periodically with the oscillation.
