A plasma shutter forming apparatus for forming a plasma shutter used in a system configured to generate and accelerate radiations by irradiating a target with a laser pulse and generating a high-density plasma for blocking the laser pulse which is returned as a feedback light to upstream of the system without being absorbed by the high-density plasma, including a plasma shutter generating target, and a plasma shutter triggering laser irradiator, wherein the laser pulse from the plasma shutter triggering laser irradiator is directed to the plasma shutter generating target to generate the high-density plasma and form the plasma shutter, thereby blocking the laser pulse which is returned as the feedback light. Optics are prevented from becoming damaged by feedback light reflecting when generating the high-density plasma in a laser-driven radiation generating system and returning back to the upstream of the laser system.