As one of the approaches to developing a monolithic integrated device, optical coupling efficiency between a monolithically integrated DFB laser and a passive waveguide is experimentally evaluated. A butt-joint coupling is selected in this study, because it is expected to produce a higher coupling efficiency than any other coupling techniques. The DFB laser is butt-jointed with the waveguide by a low-pressure MOVPE selective growth, which produces no overgrowth at the butt-joint region. The average efficiency is evaluated to be 60%. The distribution of the evaluated efficiency indicates that the coupling efficiency of more than 50% can be obtained with good reproducibility.