An apparatus includes a process chamber, a substrate holder arranged in the process chamber, a first shield provided on the peripheral portion of the substrate holder, and a second shield provided inside the process chamber. The internal space of the process chamber is partitioned into an outer space and a process space to process the substrate, by at least the first shield, the second shield, and the substrate holder. The substrate holder can be driven along a driving direction perpendicular to a substrate holding surface. The length, in a direction parallel to the driving direction, of a minimum gap portion having a minimum size in a direction perpendicular to the driving direction between the first and second shields does not change even if the substrate holder is driven in the driving direction.