Abstract: The invention provides an integrated module for optical fiber amplifiers which is able to efficiently diffuse, by a Peltier element, heat generated by an LD element outside the module, have a WDM filter component and a substrate firmly fixed for a longer period of time and further reduce the beam axis misalignment between an LD element and the WDM filter component even in a case where deformation arises at the subtrate. The part of the substrate (1), at which the Peltier element (12) is fixed, is a high thermal conductivity portion constructed of Cu or Cu-W based alloy, and at least a part of the base (11) is made into a low thermal conductivity portion constructed of Fe-Ni-Co based alloy, Fe-Ni based alloy, Fe-Ni-Cr based alloy, Fe-Cr based alloy or stainless steel, wherein the WDM filter component (5) is fixed at the low thermal conductivity portion of the base (11) by laser beam welding.