This paper plans to seek out measure to solve problems caused by the refusals of the old Aggregate Building Act to authorize constructors`` defects liability for unit owners and the right to demand compensation equivalent to defect repair for the committee of apartment dwellers representative and to find out problems and to com up with solutions to them by reviewing security deposits for defect repair and by comparing and analyzing apartment unit dealers`` defects liability. What are defects in apartment houses: two what cause defects; three, what kind of defects exist in apartment houses: four, what are the standards to judge defects: and five, who takes the responsibility to prove defects. On the basis of the results from figured out that although the Aggregate Building Act defines apartment unit dealers`` liabilities for defect repair as a legal obligation, and makes sure that not only a present unit owner as a subsequent purchaser but also an apartment unit dealer should take the responsibility for defect repair, the Superme Court does not authorize that the committee of apartment dwellers representative has the right to demand compensation equivalent to defect repair. And also lower courts have made mixed decisions for the right to demand compensation equivalent to defect repair. Thus, the chapter reviewed the issues. Which the Housing Act grants the committee of apartment dwellers representative to have, and its legality, comparing defects liability under the Aggregate Building Act. The institution of defects liability for apartment houses, inquired into the constructors and surety companies to suggest better measures. The chapter pointed out the problems caused by the recent amendment to the Framework Act on Construction Industry to shorten the extinctive period of surety obligations of Construction Guarantee. In summary, the responsibility for defect repalr by constructors should be enhanced. In addition. considerring the importance of a security deposit for defect repair. it is necessary to amend the Frame Act on Construction Industry to extend back the shortend extinctive period.