According to the methods of the present invention, energy loss and yield loss can be significantly reduced and the quality of the aluminum purity and the trace metal contents can be ensured even when used planographic printing plates are reused. A recycling material with deposited substances removed therefrom is melted in a melting furnace into a recycled molten metal. The analyzed result obtained by analyzing the recycled molten metal is used to determine the mix proportions of the recycled molten metal, a fresh metal ingot, and a trace metal master alloy to be inputted into a pre-rolling melting furnace. The produced recycled molten metal in the molten state is inputted into the pre-rolling melting furnace to be mixed with the fresh metal ingot and the trace metal master alloy.