A drain port and an exhaust port arranged at the bottom of a cup surrounding a substrate holding unit. A drainage tray is arranged below the cup so as to cover the moving area of the drain port when the substrate holding unit and the cup move in X-directions and Y-directions. An exhaust unit is arranged at a position corresponding to the position of the exhaust port of the cup when the substrate holding unit is in its spin-drying position. The exhaust unit is connected to the exhaust port to suck the interior of the cup when the spin-drying of the substrate is executed. The use of a flexible tube which is always connected to the exhaust port is no longer necessary.