Beam mode control technologies are commonly used in high-power laser welding to suppress welding defects such as spatter and porosity. Currently, laser manufacturers are proposing laser oscillators and systems with various beam mode control methods, such as fiber delivery systems and optical element systems. These technologies are applied in many fields, such as automobile bodies, EV components (motors, inverters, batteries), and electronic components. For example, it is known that welding defects such as spatter and porosity can be suppressed by adjusting the output distribution of the inner and outer beams of the ring mode beam. However, the material and size of the workpiece, laser power, welding speed, and beam mode shape are intricately related. The relationship between these welding parameters and keyhole and molten pool behavior is complex, and the detailed mechanisms of porosity and spatter suppression remain unclear. In this study, bead-on-plate welding was performed on stainless steel using a ring-mode profile formed by a diffractive optical element for high-power fiber lasers developed by Furukawa Electric. The laser power ratio of the inner and outer beams in the ring mode, the size of the outer frame, and the beamline width were controlled. The keyholes and molten pools formed were observed with a high-speed camera. Finally, the effects of beam mode parameters on weld quality in bead-on-plate welding of stainless steel were discussed.