Disclosed is a group III nitride semiconductor light-emitting device which suppresses electric current concentration in a light-transmitting electrode and a semiconductor layer directly below an electrode to enhance light emission efficiency, suppresses light absorption in the electrode or light loss due to multiple reflection therein to enhance light extraction efficiency, and has superior external quantum efficiency and electric characteristics. A semiconductor layer (20), in which an n-type semiconductor layer (4), a light-emitting layer (5) and a p-type semiconductor layer (6) are sequentially layered, is formed on a single-crystal underlayer (3) which is formed on a substrate (11). A light-transmitting electrode (7) is formed on the p-type semiconductor layer (6). An insulation layer (15) is formed on at least a part of the p-type semiconductor layer (6), and the light-transmitting electrode (7) is formed to cover the insulation layer (15). A positive electrode bonding pad (8) is provided in a position A corresponding to the insulation layer (15) provided on the p-type semiconductor layer (6), on a surface (7a) of the light-transmitting electrode (7). A sheet resistance of the n-type semiconductor layer (4) is lower than a sheet resistance of the light-transmitting electrode (7).