With its specialty, many events have happened during construction project and these have resulted in increasement of contract amount and prolongation of contract period. In case of contract delay caused by the Owner, the Contracts are entitled to claim the cost of the delay in accordance with the Government Bid and Contract Administration Guideline. Many delay claims which are not precisely defined are asked by the Contractor and these made many problems. Therefore delay claims in U.S.A are compared with our country. And five directions were suggested in this study. Application of the basis of actual cost calculation, permission of unabsorbable idle labor cost and overhead expenses, proof liability of actual cost, treatment of concurrent delay cost.