A rough-polishing method for conducting a rough polishing before mirror-finish polishing on a semiconductor wafer using a polishing apparatus includes a first polishing step for polishing the semiconductor wafer using slurry containing colloidal silica supplied by a slurry supplying unit and a second polishing step for polishing the semiconductor wafer using alkali solution provided by mixing deionized water supplied from a deionized-water supplying unit and alkali concentrate solution supplied by an alkali-concentrate-solution supplying unit. The pH value of the alkali solution and polishing time in the second polishing step are determined based on the load current value of the polishing table in the first polishing step.