In Indonesia banks can operate either conventionally or by principle of profit sharing. In practice, banks using conventional system can develop better in comparison with banks using sharing profit system. Legal instruction given by MU which prohibited bank interest quantitatively did non influence the credibility of relationship toward bank operating conventionally, the influence that may exist is the psychological one. In this case one thing that is necessary to be paid attention to in order that syariah banks can develop well is to increase the credibility of their relationship by the support of Indonesian Bank as the regulator of banks in Indonesia.