Purpose: Since the facility guidelines for National Designated Isolation Unit wards(NDIUs) had been edited since 2016, all hospital who want to expand or install NDIU should adapt the new guidelines. Instead of providing area requirement, by the way, only essential or optional facility requirements are suggested except patient bedroom in the guidelines. So, as analyze area and area composition of the NDIUs, it could be expected that this study has a role as an area planing reference for not only NDIU but also another airborne infection isolation room. Methods: For the area analysis, 18 sample hospitals are selected among 2016 year applicants. All rooms in NDIUs are grouped as zones whether those are negative air pressurized or not and programed room or not. At the end, area of the zones are summarized and analysed a relationship between area increase and bed number by both correlation analysis and regression analysis. In addition, department usable and gross area per bed, N/G ratio, G/N ratio, and average area ratio of each zone is calculated. Results: First of all, rooms in none negative air pressurized zone of the NDIUs haven't shown a regular installation so that only those in negative air pressurized zone are targeted for the area analysis. Second of all, patient room unit(0.92) and support area(0.79), by correlation analysis, are correlated with total net area. Patient room unit(0.94) and total net area(0.79) are also shown a correlation with bed number. Department usable area($R^2=0.63$, y=36.278x + 102) and patient room unit area($R^2=0.89$, y= 27.993x - 0.8924) has a relationship with bed number by regression analysis. Average N/G is shown as 0.85 and G/N 1.36. Average area ratio of circulation, doffing area, patient room unit, and support area are 25.4%, 9.1%, 50.9%, and 14.6% in order. Implications: This study is a basic research for exploring the NDIUs guidelines to find resonable evidence to develop it for its practical use. Still, it is possibly expected that the guideline is to be developed by post occupancy evaluation in the area of where minimum requirement or facility grade needs to be defined, and by further studies with various perspectives.