A fiber laser and an optical device for controlling polarization and outputting single polarized light are provided in a simple structure. The fiber laser includes a solid-state laser fiber (3) doped with a rare earth element, a pump light source (1) for exciting the solid-state laser fiber, a reflective element (2) having wavelength dependency, and a wavelength conversion element (4) arranged at the output side of the solid-state laser fiber away from the reflective element at a specified distance along the solid-state laser fiber, in which an end face of the wavelength conversion element (4) is inclined to an optical axis.