PURPOSE: To restrain the temperature rise of a mask or a pattern, etc., from occurring for reducing the high load due to thermal stress and the slip in a pattern by a method wherein the pattern is intermittently exposed to an irradiated element through the intermediary of the mask.

CONSTITUTION: When the transient deformation process due to the thermal damage resultant from the exposure of a mask and an irradiated element is mathematically analyzed to divide the exposure time τg (t) e.g., into ten each of rectangular pulse rows and further to be intermittently exposed in the period τp longer than the pulse width Δτg, the temperature rise per pulse is reduced to restrain the thermal stress and expansion resultant from the temperature rise from occurring. Through these procedures, the irregular deformation of a pattern on the mask e.g., in case of exposing to a wafer can be restrained from occurring to enhance the patterning precision.