A substrate processing apparatus includes a substrate holding stage to hold a substrate having a surface facing up, the substrate having an exposed and developed resist pattern over the surface, a rotation driving mechanism to rotate the substrate holding stage around a vertical axis, a solvent vapor discharge nozzle having a discharge hole capable of discharging solvent vapor to swell the resist pattern onto the surface of the substrate and a vacuum opening capable of absorbing the solvent vapor discharged from the discharge hole, and a moving mechanism to move the solvent vapor discharge nozzle from an edge to a center of the substrate. The substrate is rotated around the vertical axis while moving the solvent vapor discharge nozzle from the edge to the center of the substrate, discharging the solvent vapor from the discharge hole, to supply the solvent vapor over the substrate in a spiral manner.