Because of the characteristics of public construction project, there are many cases of contract change or change orders during the construction. The contract change is accompanied by not only direct expenses but also time extension caused of budget securing problem, etc. during the project, so it increases problems such as the increase of indirect expenses, etc. Therefore, this study drew 7 indexes which can quantify effects and loss made by contract change on construction cost and construction period and inspected and inspected/analyzed adjustment of contract occurred at the stage of construction and occurrence situation by reasons of time extension for pubic cultural sports facilities whose estimated expenses are more than 10 billion. As the result, among the adjustments of contract, construction expenses are greatly increased in case of huge construction, the lowest expenses method and continuous non-construction. And, construction expenses of average 8.8% were increased by change orders of three and four times per a case. The construction period was greatly increased in case of huge construction, turnkey method and long-term continuous construction, so time of average 25.3% per a case was expanded. In this study, contract change at the stage of construction is influenced by systematic inspection, successful bid, contract characteristics, etc. at the stage establishing designing quality and fundamental plan by orderer. Through the minute inspection and additional supplementation for the various reasons, this study will be applied to discriminate and manage Cost Overrun Risk in the future.