A settlement system is provided for an electronic cashing card such as an IC card, a prepaid card, or the like. A card comprises a memory storing process data to execute a settlement under a condition of matching a personal authentication. Also, a memory stores process data to execute a settlement without matching a personal authentication. When settlement is executed with authentication processing, an authentication balance stored memory is updated to the amount of the balance after the settlement. A non-authentication balance stored in memory is updated to an amount of money equal to or smaller than the authentication balance. When executing a settlement, the non-authentication balance is compared with the authentication balance. It is determined that an illegal process has been executed with the card when the non-authentication balance is larger than the authentication balance.