An exposure apparatus includes a projection optical system for projecting a pattern of a mask onto an object using a light with wavelength of 20 nm or less from a light source, and first and second accommodating parts for accommodating the projection optical system and the mask or the object, said first and second accommodating part has different pressures, wherein said a Ps/Po.gtoreq.100 and Ps.ltoreq.10.sup.-3 Pa are met, where Po is the pressure of the first accommodating part, and Ps is the pressure of the second accommodating part.