The banking business activities held by many government bank, private bank, and multinational bank often play a role in practice of standard contract within their banking products, which are saving, bank credit, check, and time deposit services. The implementation of standard contract which often used by bank, however, give many benefits for the bank in time value and the easiness to deal with the customer in massive count, who need to make a contract with bank in order to use those banking products. The problem arises when the bank often take the benefit from the standard contract practice to make the term and condition in the contract which is more likely to give a better legal protection for the bank affairs than the banking customer affairs. In this case, that practice was found on check account contract of Bank Mandiri, which gives unequal position between the bank and the customer. Usually, the Bank always gets the good benefit from it because they make the whole content of the contract by themselves without looking for any customer’s aspiration. Therefore, the purpose of this legal research is to observe and find out if the content of Bank Mandiri check account contract especially in the term and condition section is based on regulation of Law Number 08 of 1999 concerning Consumer Protection and other regulation of Bank Indonesia concerning the Banking Customer Protection. The result of this legal research will demonstrate if the content of the check account contract of Bank Mandiri are having a strong legal standing over the law of customer protection and banking regulation, thus may assist the banking customer to know the similarities between the legal protection by the law and their legal protection in the contract. So, the benefit for the account owner is in case of they are having a dispute with the bank, thus, they can protect their right as a consumer over the law of consumer protection.