A nitride-based semiconductor device according to the present disclosure includes a nitride-based semiconductor multilayer structure 20 with a p-type semiconductor region, of which the surface 12 defines a tilt angle of one to five degrees with respect to an m plane, and an electrode 30, which is arranged on the p-type semiconductor region. The p-type semiconductor region is made of an AlxInyGazN (where x+y+z=1, x≧0, y≧0 and z≧0) semiconductor layer 26. The electrode 30 includes an Mg layer 32, which is in contact with the surface 12 of the p-type semiconductor region, and a metal layer 34 formed on the Mg layer 32. The metal layer 34 is formed from at least one metallic element that is selected from the group consisting of Pt, Mo and Pd.