A submount with an electrode layer having excellent wettability in soldering and method of manufacturing the same are disclosed. A submount (1) for having a semiconductor device mounted thereon comprises a submount substrate (2), a substrate protective layer (3) formed on a surface of the submount substrate (2), an electrode layer (4) formed on the substrate protective layer (3) and a solder layer (5) formed on the electrode layer (3) wherein the electrode layer (4) is made having an average surface roughness of less than 1 μm. The reduced average surface roughness of the electrode layer (4) improves wettability of the solder layer (5), allowing the solder layer (5) and a semiconductor device to be firmly bonded together without any flux therebetween. A submount (1) is thus obtained which with the semiconductor device mounted thereon is reduced in heat resistance, reducing its temperature rise and improving its performance and service life.