An AlN buffer layer 2; a silicon (Si)-doped GaN high-carrier-concentration n⁺ layer 3; an Si-doped n-type Al_0.07Ga_0.93N n-cladding layer 4; an Si-doped n-type GaN n-guide layer 5; an active layer 6 having a multiple quantum well (MQW) structure, and including a Ga_0.9In_0.1N well layer 61 (thickness: about 2 nm) and a Ga_0.97In_0.03N barrier layer 62 (thickness: about 4 nm), the layers 61 and 62 being laminated alternately; an Mg-doped GaN p-guide layer 7; an Mg-doped Al_0.07Ga_0.93N p-cladding layer 8; and an Mg-doped GaN p-contact layer 9 are successively formed on a sapphire substrate. A p-electrode 10 is formed of a film of titanium nitride (TiN) or tantalum nitride (TaN) (thickness: 50 nm). The contact resistance of this electrode is reduced through heat treatment.