Abstract: A surface-emitting semiconductor optical device is provided, which has a high external quantum efficiency and a high coupling efficiency with an optical fiber. This device has a multilayer device structure including an optical absorption layer formed by a semiconductor substrate, a semiconductor mirror layer, a first (n- or p-type) semiconductor cladding layer, a semiconductor active layer, a second (p- or n-type) semiconductor cladding layer, and a current spreading layer formed by a transparent and doped semiconductor wafer. These layers are stacked along a stacking direction of the device structure. The absorption layer is located at a first end of the body. The active layer is sandwiched between the first and second cladding layers. The mirror layer is located between the first cladding layer and the absorption layer, and serves to reflect the light generated by the active layer toward the current spreading layer.