Provided is a method of manufacturing a ridge waveguide type semiconductor laser diode, the method including sequentially forming, on a substrate, a lower clad layer, an active layer, a first upper clad layer, and a second upper clad layer; forming an insulating mask on the second upper clad layer; wet-etching the second upper clad layer by using the insulating mask to form channels passing through the second upper clad layer and a ridge between the channels; and performing dry-etching by using the insulating mask to form trenches that are extended from the channels and pass through the first upper clad layer.