The present invention relates to a laser diode for optoelectronic integrated circuit, more specifically, to a laser diode for optoelectronic integrated circuit with a rooftop reflector which can be operated by means of a low driving current and a process for preparing the same. A laser diode for optoelectronic integrated circuit of the present invention comprises: a substrate; a waveguide consisting of a N-cladding layer and a passive waveguide layer, which is positioned on the substrate; an active waveguide with a rooftop reflector, which is positioned on the waveguide and has an epitaxial layer of a separating layer, an active layer, a P-cladding layer and a p-ohmic layer; SiO.sub.2 layer with a linear contact opening which is positioned on the active waveguide; an upper metal contact layer which is positioned on the SiO.sub.2 layer; and, a lower metal contact layer which is positioned under the substrate. The laser diode for optoelectronic integrated circuit of the present invention has a high efficiency of utilization of light and a low threshold current, to make the laser diode operational by means of a low driving current.