A laser diode includes an active layer, a strip-shaped ridge provided above the active layer, a pair of resonator end faces sandwiching the active layer and the ridge from an extending direction of the ridge, and an upland section provided being contacted with both side faces of the ridge in at least one of the resonator end faces of the pair of resonator end face and in the vicinity thereof. A thickness from the active layer to a surface of the upland section is larger on the resonator end face side and is smaller on a central side of the ridge, and the thickness is continuously changed from a thick portion on the resonator end face side to a thin portion on the central side of the ridge.