The present invention provides a radiation blocking unit including: an attachment member that is attachable between sources and an object table surface to which radiation from a radiation source and visible light from a visible light source are emitted, the sources including the radiation source and the visible light source a radiation blocking portion, disposed on the attachment member, that transmits the illuminated visible light to an overlapping incidence region on the object table surface in which an incidence region of the radiation and an incidence region of the visible light overlap, and that blocks the irradiated radiation outside the overlapping incidence region and a visible light blocking portion, disposed on the attachment member, that transmits the irradiated radiation to the overlapping incidence region, and blocks the illuminated visible light outside the overlapping incidence region.
