In the semiconductor laser diode, a first material layer, an active layer, and a second material layer are sequentially formed on a substrate, a ridge portion and a first protrusion portion are formed on the second material layer in a direction perpendicular to the active layer, the first protrusion portion being formed at one side of the ridge portion, a second electrode layer is formed in contact with a top surface of the ridge portion, a current restricting layer is formed on an entire surface of the second material layer and exposes the second electrode layer, a protective layer is formed on a surface of the current restricting layer above the first protrusion portion and has an etch selectivity different from that of the current restricting layer, and a bonding metal layer is formed on the current restricting layer and the protective layer in electrical connection with the second electrode layer.