A slit nozzle is moved by a nozzle lifting/lowering mechanism and a nozzle sliding mechanism relative to substrates held in a substantially horizontal attitude by spin chucks. A development liquid is discharged on each substrate from a discharge port of the slit nozzle such that development processing for the substrate is performed. After the development liquid is discharged, the slit nozzle is moved to a waiting position excluding positions over the substrates held by the spin chucks. In waiting pods provided at the waiting positions, cleaning processing for the slit nozzle is performed by a cleaning liquid with gas bubbles mixed therein.