The Korean Supreme Court in its judgment of 14, January 2010(2007Da55477) made the decision that the principal (defendant) is liable for paying recovery to the manager (plaintiff) for his outlay. In this case the manager carried on the principal`s affair with the expectation of entering into contract between them. Korean Supreme Court denied the completion of contract but acknowledged negotiorum gestio. And the Korean Supreme Court allowed the manager`s claims for remuneration for services rendered by negotiorum gestio. So there should be no difference between claims for reimbursement of expenditures spent and claims for remuneration for services rendered. In principle the duty to benefit (remuneration) must be supported by contract. In this case it is not impossible but hard to recognize the completion of contract by means of normative interpretation or realization of intent. If the Korean Supreme Court has divided the contract and negotiorum gestio rigidly and has insisted that the remuneration could not arisen from negotiorum gestio, the Korean Supreme Court must demonstrate the completion of contract to accomplish sanctioning defendant, and this needs huge effort, If the defendant doesn`t have duty to pay the remuneration, defendant`s opportunistic behavior wasn`t sanctioned, the admission of remuneration by negotiorum gestio removes ambivalence of the result which might have arisen out of the difference of legal composition. So this process can reduce the cost of argumentation. In this point the negotiorum gestio has a function of mitigation of cost of argumentation (such as the actual contractual relationship. A part of literature opposes to extend the scope of application of negotiourm gestio. The main reason of this opinion is that the negotiorum gestio is rooted in altruism. But the historical review revealed that the main function of negotiorum gestio is allocation of goods. So it is porper to extend the scope of application of negotiourm gestio.