Abstract: A laser apparatus capable of very effectively converting excitation light to laser oscillation light includes a single continuous long laser fiber wound by multiple turns and made immobile by an ultraviolet setting resin as to form a cylindrical shape conglomerate whose opposite ends are exposed as outputs for laser beam, and generates a laser oscillation light from the opposite ends upon radiation of excitation light from a periphery of the fiber. The laser fiber has a clad covering a core, which is doped with active lasing substances such as Nd.sup.3+ ions.