PURPOSE: To eliminate the influence of a variation in two surface states by detecting a static pressure between the two surfaces by a static pressure bearing mechanism for supplying pressure fluid of predetermined supplying pressure to a gap between the two surfaces or regulating the gap between the two surfaces in response to information obtained by measuring the flow rate of the fluid.

CONSTITUTION: The static pressure of a force detection meter 8 for a predetermined gap value when fluid of predetermined supplying pressure is injected from a nozzle 9 is obtained in advance, and a predetermined input is set. The fluid of the predetermined pressure is actually injected from a pressure chamber 14 through the nozzle 9 to the surface of a wafer element 1. The element 1 is elevationally moved by a Z-axis drive table 4 to vary a gap between the element 1 and an exposing mask 5, thereby altering the static pressure. In this case, a static pressure generated between the static pressure surface of a mask holder 6 and the element 1 is detected by the meter 8, a predetermined input is set, a fine driving mechanism 7 is so driven as to match it to the static pressure completely set at the predetermined input to finely adjust the gap between the element 1 and the mask 5.