Energy source diversification through development of coalbed methane (CBM) resources is one of the key strategies to make a country less dependent on simple energy resources (e.g., crude oil, natural gas, nuclear energy etc.). Especially, enhanced coalbed methane (ECBM) technology can be expected to secure the resources as well as environmental benefits. However, the raw CBM gas obtained from CO2 ECBM contains a considerable amount of CO2, and the CO2 content increases depending on the operation time of the facility. Considering the changes of the CBM composition, we developed process simulations of the CBM separation & purification processes based on the amine absorption to meet the design specifications (CH4 purity of product stream: 99%, CH4 recovery rate: 99%) with different CBM feed gas conditions. Using the developed simulation model, we performed an economic evaluation using unit methane production cost (MPC) considering coal-swelling types and facility operation time, and established an operatio strategy under different natural gas market scenarios.