An apparatus projects a pattern formed on an original plate onto a substrate through a projection optical system and liquid in a state where a gap between the substrate and a face of the projection optical system is filled with liquid. The apparatus includes a movable substrate stage to hold the substrate and including at least a mark unit or a measurement unit having a light-receiving unit, a determination device to determine whether the liquid is attached to the mark unit or the measurement unit, and a liquid supply device to attach liquid to at least the mark unit or the measurement unit before the attached liquid is air-dried if liquid is determined to be attached to the mark unit or the measurement unit.