The present invention relates to a fixed interest payment system for a real estate investment product purchased through online, which is capable of guaranteeing a fixed interest payment to a purchaser purchasing a specific real estate investment product for a predetermined period. The fixed interest payment system according to the present invention includes : a web server of a financial company; a web server of a real estate management company; and at least one or more of user terminals configured to purchase the real estate investment product through the web server of the financial company via an Internet network and set an interest return option and a contract expiration option of the real estate investment product. In a case in which a user of the user terminals purchases the real estate investment product, the web server of the real estate management company, when conducting a real estate transactions between the user of the user terminal and the financial company, receives corresponding predetermined fees for trade consultation from each of the user of the user terminal and/or the financial company.(100) Web server of a real estate management company(200) Database of a real estate management company(300) Web server of a financial company(400) Database of a financial company(500) Web server of a developer(600a, 600n) User terminal(700) InternetCOPYRIGHT KIPO 2017