Hydrogen is an essential element as an energy carrier in the hydrogen economy. In order to mass-produce hydrogen, a High Temperature Gas-cooled Reactor (HTGR) cogeneration system coupled with hydrogen production process and electricity generation has been considered as the most effective method to produce hydrogen. Even if an HTGR cogeneration system is technically capable of supplying a mass amount of hydrogen, it is uncertain that the HTGR cogeneration system can compete with other hydrogen production technologies. Therefore, it is important to evaluate the economic competitiveness of the HTGR cogeneration system. In this paper we developed a process flow diagram for the cogeneration system to maximize hydrogen productivity in Steam Methane Reforming (SMR) hydrogen production processes in conjunction with electrical generation systems in a 350MWt HTGR. Economic analysis and ripple effect estimation were conducted for the self-developed process model using Benefit to Cost ratio (BC ratio) and an inter-industry table. The results of the quantitative analysis show that the HTGR cogeneration system is economically competitive and can be used as basic data for commercial HTGR construction in the future.