Provided is a passive containment air cooling device with an isolated pressure boundary, including a heat exchanger positioned inside and outside a containment, penetrating through an outer wall of the containment to be connected to the containment through a pipe and thus form a closed loop, and including a coolant, an air induction duct circulating air outside the heat exchanger, and a cooled air exhaust unit formed in the air induction duct to increase cooling efficiency of the heat exchanger.