The present invention relates to a credit rating method and a system thereof. In particular, the present invention relates to the credit rating method and the system thereof which can conduct credit ratings of companies that do not have a business relationship with a financial institution, or companies or organizations maintaining a business relationship with a company that cannot receive credit information from an external credit information provider, and more particularly, to the credit rating method and the system thereof which can conduct credit ratings of companies that commonly carry out transactions on credit. According to an embodiment of the present invention, the credit rating method comprises a step of inputting, to a database, the transaction date, types of transaction goods or services, a transaction volume, a transaction amount, an agreed payment date of the transaction amount, the payment date of the transaction amount, a payment amount of each transaction for each company, and days of late payments and amounts of late payments when the agreed payment date has passed. According to one feature or a combination of multiple features of the present invention, it is possible to obtain a tool for conducting credit ratings by utilizing transaction information with a relevant company. In particular, the present invention can consider sales performance and late payment information so as to obtain a useful index for credit ratings in view of transactions. In addition, the present invention enables an early warning rating to be appropriately determined by considering the external credit rating fluctuation and the real estate right fluctuation situation of a company.(AA) Transaction book(BB) Internet(CC) NICE rating system(DD) KED company information system(EE) Real estate systemCOPYRIGHT KIPO 2019