Experimental adsorption measurements for one shale sample were conducted at 25 degrees C, 50 degrees C and 75 degrees C up to 2,000 psia by using pure methane (CH4) and pure carbon dioxide (CO2) to understand the behaviour of CH4 and CO2 adsorption on shales. The effects of temperature and pressure on CH4 and CO2 adsorption on the shale sample were observed. When temperature decreases from 75 degrees C to 25 degrees C, the adsorption capacity increases for both CH4 and CO2 adsorption. As pressure increases, adsorption capacity increases then become constant for CH4 adsorption. However, for CO2 adsorption, adsorption increases with pressure until certain value then it decreases suddenly. By using experimental adsorption capacities, adsorption behaviour of shale gas reservoirs was observed.