Cleaning and drying of semiconductor wafers is carried out in a single-chamber type cleaning/drying apparatus for flat objects such as semiconductor wafer, where cleaning is carried out by impinging both sides of the wafer which rotates at a relatively low speed with jets of a washing liquid and where subsequent drying is carried out in the same chamber by increasing the rotation speed of the wafer and supplying an isopropyl-alcohol (IPA) mist onto the wafer from the top of the chamber. After the IPA forms a solution with the residue of water on the wafer, the drying process is accelerated by supplying gaseous nitrogen through nozzles arranged on both side of the coaxial with the wafer center. As a result, the IPA-water solution quickly evaporates without leaving traces of water drops on the dried surface.