[Object] An object of the invention is to provide a laser device having high optical amplification efficiency.[Solving Means] A laser device 100 includes: an optical fiber 20 which includes a core 21 and a clad 22 and through which seed light and pumping light propagate; and a glass rod 50 which is doped with rare earth elements, has a diameter larger than that of the core 21, wherein the seed light and the pumping light output from the optical fiber 20 are input to the glass rod 50 to have increased diameters, and output light including at least the amplified seed light is output from the glass rod 50.