A few years ago, The Supreme Court of Korea gave a decision upon the use of KT card(deferred payment telephone card issued by Korea Telecom), denying unlawful use of facilities for convenience(§348-2) and admitting unlawful uttering of private document(§236). I think that the argument of the decision is not appropriate in two points of view. First of all, It is not rational to admit unlawful uttering of private document. When we use KT card in public telephone, only magnetic stripe of the card is uttered. Criminal Act of Korea has a provisions to punish falsification or alteration of electromagnetic records(§227-2, §232-2), uttering falsified or altered electromagnetic records(§229, §234) and unlawful uttering of official or private document(§230, §236). But the Act does not have a provision to punish unlawful uttering of electromagnetic records. Secondly, unlawful uttering of KT card should be valued not only from social point of view but individual point of view. It is very important value to protect individual property as well as to protect social reliance on document. In this case, the accused uttered other person's KT card without paying price, acquired benefits to property and caused loss to telecomunication service provider or the owner of KT card. For that reason, I think it is needed to admit unlawful use of facilities for convenience in this case.