An exposure apparatus having a projection optical system and configured to expose a substrate to light via a pattern of a mask and the projection optical system. The apparatus includes a chamber to hermetically contain at least part of the projection optical system, and a circulating system to send an inert gas to the chamber. A controller controls a temperature regulator on the basis of a target temperature in the chamber and a detection result of a temperature sensor. The controller changes the target temperature so that a timewise temperature gradient of the inert gas falls within an acceptable range. The acceptable range is determined so that a timewise change in pressure in the chamber caused by a timewise change in temperature of the inert gas is within an acceptable range.