To prevent the deterioration of a shutter vane due to exposure light while satisfying the brightness requested to the shutter vane by providing at least 2 kinds of shutter vanes as light shielding means which can be used separately depending upon the length of light shielding time.

A shutter vane 4 is provided between a shutter vane 3 and a light source lamp 1. At the time of exposure, if it is required to control the shielding light in a short duration accurately at a high speed as in the case of the repetitions of exposure and movement of the wafer, the shutter vane 4 is displaced from the optical path, and the shutter vane 3 is used for shielding light. If light has to be shielded for a long time as in the case of wafer or reticle replacement, light is once shielded with the shutter vane 3 and then the shutter vane 4 is place in the optical path for shielding light thereby preventing the exposure of the shutter vane 3 for a long time. When performing the exposure again, the shutter vane 4 is displaced from the optical path immediately before the exposure. By doing this, the time required for exposure can be reduced and the productivity of the semiconductor element can be enhanced.