An optical fiber part includes an optical fiber having a main fiber, a taper fiber and a small-diameter fiber. The core diameter of the taper fiber decreases along an optical axis. Further, a heat-radiation silicon adhesive that is a highly heat-conductive material having heat conductivity of 4 W/mK or higher has been applied to the entire area of the outer circumference of the taper fiber and a part of the small-diameter fiber next to the taper fiber. An input end of the optical fiber is connected to a semiconductor laser having an output power of 10 W. Light output from the laser propagates through the optical fiber and output from the output end. A part of light that has propagated through the main fiber and entered the taper fiber is output through the cladding thereof. Heat generated by light output from the cladding is transferred through the heat-radiation silicon adhesive and radiated.