The present invention relates to a real estate brokerage and real estate business method using an integrated real estate information system. The present invention includes : a brokerage client registration step of making a brokerage request from a brokerage client online and registering the brokerage client inputted from a broker UI; a brokerage progression step of recording and managing the brokerage progression of the registered brokerage client; a contract processing step of making progress on a contract of the brokerage client; a sales processing step of automatically calculating the completion of balance payment and the deposit of brokerage commissions, and payment for co-brokerage after the contract of the brokerage client; a tax invoice issue step of generating and issuing a tax invoice for the deposited commission and transmitting the invoice to the National Tax Service; a transaction reporting step of generating and reporting a real estate transaction return for the real estate trade contract and transmitting the return to the Ministry of Land, Infrastructure, and Transport; and a settlement and completion step of paying benefits to a licensed real estate agent responsible for the contract and brokerage of the brokerage client and a person in charge of the corresponding property, paying brokerage commissions and traffic expenses to the co-brokerage real estate agent, and completing the client account of the brokerage client.