Mutually different plural kinds of processing liquid are sequentially supplied to a gap space in which a substrate is arranged to perform a wet processing to the substrate with respect to each processing liquid. Further, the processing liquid used in the wet processing is sequentially released from the communicating portion upon execution of each wet processing. The liquid retrieval tanks are selectively positioned at a retrieval position corresponding to the kind of processing liquid released from the communicating portion by relatively moving the processing unit and the liquid retrieval unit. The liquid retrieval unit is separated from the processing unit and is arranged below the processing unit. The processing liquid is released from the communicating portion of the processing unit to below the gap space downwards vertically.