A substrate processing apparatus has an indexer block and a processing block. One side of the processing block has a vertical stack of a plurality of top surface cleaning units and the other side of the processing block has a vertical stack of a plurality of back surface cleaning units. Reversing units for reversing the substrate W are provided one above the other between the indexer block and the processing block. For example, one reversing unit is used for reversing the substrate before a back surface cleaning processing by the back surface cleaning unit or for other purposes, and the other reversing unit is used for placing the substrate W after a top surface cleaning processing by the top surface cleaning unit or for other purposes.