A high power semiconductor laser device includes a semiconductor substrate, a lower clad layer formed on the semiconductor substrate, a lower guide layer formed on the lower clad layer, an active layer formed on the lower guide layer, an upper guide layer formed on the active layer, and an upper clad layer formed on the upper guide layer. The lower and upper clad layers have the same refractivity. The lower clad layer includes a high refractivity layer, which is spaced from the lower guide layer by a constant distance, and has a refractivity higher than that of the upper clad layer.