PURPOSE: To provide a hand piece that has a light transmission part which does not use a high molecular compound by projecting an optical fiber at the end of the hand piece, and forming a removable guide means by which the projected optical fiber is held in a curved shape.

CONSTITUTION: This hand piece 100 comprises a grip 10 which is a hand-piece main body; an optical fiber 20 for guiding a laser beam from a laser beam source and for guiding the laser beam into the hand piece; an optical fiber 30 joined with the optical fiber 20 to apply the laser beam to a portion for treatment, that is, a portion for illumination; and a guide member 40 which holds the optical fiber 30 in a curved shape. The guide member 40 can be attached to and removed from the end of the hand piece 100. The laser beam source is an infrared laser beam source whose wavelength is in the vicinity of 2.9μm, and the optical fibers are either zirconium fluoride glass fibers or anhydrous quartz fibers.