The case which in this article tried to research is about the effect of share transfer security contract. The petitioner A loaned the corporation and made a contract of security by means of transfer for half the total outstanding shares with the corporation. When corporation didn`t perform its debt, the petitioner demanded to record his name in the register of shareholders, however it was denied. Moreover the secured shares were transferred to B and B held shareholders meeting and board directors and became a representative director. In this case the issue is who should be the owner of the secured shares after the time for performance of the claim secured. The owner might be changed according to the theory of share transfer security. If we rely on the theory that ownership of secured shares be belonged to the creditor in trust and after the due time of debt he obtain the ownership definitely, then A would be the owner of secured shares. On the other hand, there is another theory that creditor should hold the mortgage right to the secured shares throughout the hole period of debt. The court has applied the former theory to the share transfer security. The Supreme Court might not have had same opinions on share transfer security. In this case the Supreme Court found that A (creditor) was the owner of the secured shares after the time for performance. Recently the Court found that when the appraisal amount of secured shares would be higher than debt, the creditor has the duty of adjustment after the due day and he has to back the residual amount to debtor. On the contrary when the appraisal amount of secured shares would be lower than debt, then he has to inform about that to debtor. After such a adjustment he could be owner of the secured shares. In this case the reasoning of the decision has some discordance with the former decision. It would be needed to try to find evident standards of reasoning about how to decide the owner of secured shares after the due day of debt in share transfer security.