An object of the present invention is to provide a panel manufacturing method capable of easily adapting to manufacture of panels, such as door panels, of different sizes. The present invention provides a panel manufacturing method for a panel made of an outer plate integrated with an inner plate. The method includes a step of applying an adhesive to a predetermined place on the outer plate; a step of mating the outer plate and the inner plate with each other and providing preliminary bonding by laser welding; a step of hemming by bending an outer edge portion of the pre-bonded outer plate to wrap over a circumferential edge portions of the inner plate and then pressing flat; and a step of sealing the panel, after the outer plate has undergone the hemming step on its circumferential edge portions, by applying an adhesive.