[A forecast of demand and supply of the energy in Korea with demographic change] This report is one of the series ‘the development of forecast model for the demand of legislation and policy’ and studies on the demand and supply of Energy in Korea from year 2010 to 2100. This model is developed using system dynamics modeling technique， and perform the simulation with some scenarios. The most important insight from the simulation results is that the demand of primary energy and final energy will decreased after the peak of year 2027 and final energy consumption will be equal to current one in 2060. The capacity factor of power plants will reach the peak in 2025 at the 79％ and then decrease to about 60％. Vehicles demand will reach the peak in the early 2030s and the registry number will be 22 millions. The demographic change will have impacts on the followings. Firstly， the financial problems of generation companies will arise with the decrease of capacity factor of power plants. Secondly， strategy of R&D in the energy field will be required to change because of the reduction of new demand of energy facility. Lastly， the security and safety issues in electricity and gas industries will be more important than now with scale-up of the network system.