Laser beam welding is widely used for several industries such as automobile industry, nuclear power plant industry, petrochemical industry and so on, because it is excellent in remote control and automation and enables high-quality welding with a smaller heat-affected zone than other welding. Generally, when a metal is irradiated by a high-power laser, a spatter is generated when the laser is irradiated, and the spatter is one of factors in defects such as a weld wall thinning and a porosity. In our previous study, it has been found that the spatter generation is due to fluctuation of the keyhole while laser irradiation. In this study, multi-spot laser was employed in laser beam welding for development of spatter free process, it was clear the effect of multi spot laser on spatter suppression.    The longitudinal cross-section of the molten pool was directly observed using the glass transmission method to measure the temporal variation of the molten pool area in keyhole welding with high power laser. A disk laser was employed with a maximum output power of 16 kW and a wavelength of 1030 nm. A bead-on-plate welding test was conducted for the specimen, when the SS304 specimen butted against glass plate was set in a chamber. As the results, the 3-spot laser welding was minimized to generate spatter in keyhole welding, it was found that the suppression of fluctuation for molten pool.