To produce high concentration of hydrogen, steam-methane reforming reaction was carried out by using sorption enhanced reaction process. Cahn balance was used to check CO2 adsorption capacities of the CO2 adsorbents which could be applicable to the sorption enhanced reaction process at high temperature, and K2CO3/hydrotacite was selected as the most suitable CO2 adsorbent at the high temperature. The K2CO3/hydrotalcite showed a high CO2 adsorption capacity as much as 0.575 mmol/g at 450 ℃ and 0.3 atm of CO2 pressure because of its increased basicity and pore structure modification by K2CO3 impregnation. In the steam-methane reforming reaction using Ni/Al2O3 catalyst without CO2 adsorbent at 500 ℃, there was catalyst deactivation due to excess amount of steam in case of 6:1 steam and methane ratio, but there was a suitable catalyst activity such as 40.9% H2, 48.4% CH4, 10.7% CO2, and 0.35% CO of product composition for 3:1 reactants ratio. In the sorption enhanced reaction process using a reactor packed with the catalyst and the CO2 adsorbent simultaneously, high concentration of hydrogen above the equilibrium was generated via CO2 adsorption by the adsorbent, and the maximum concentration of hydrogen was 84.8% and the hydrogen yield was 67.1% until by-product CO2 broke-through.