PURPOSE: To enable irradiation of a light having a constant intensity over the entire area of an object to be irradiated when a synchrotron radiation is swung in the vertical direction by putting a reflection mirror close to or apart from an electron storage ring in accordance with an incident glancing angle of the light to the reflection mirror.

CONSTITUTION: A concave smooth reflection surface 12a of a reflection mirror 12 is irradiated with synchrotron radiation 11 emitted from an electron storage ring 10, and the radiation light 11 reflected on the reflection mirror 12 is radiated to an object to be irradiated. The reflection mirror 12 is put close to a ring 10 along the light axis 11a of the radiation light 11 in accordance with an increase in an incident glancing angle θ of the radiation light 11 to the reflection surface 12a and put apart from the ring 10 along the light axis 11a in accordance with a decrease in the incident glancing angle θ. Thus, when the radiation light 11 is swung by changing the glancing angle θ in the vertical direction to irradiate the entire area of a substrate 20, the radiation light 11 always forms an image on the substrate 20 by moving the position of the reflection mirror 12 along the light axis 11a.