Decomposition of calcium carbonate in the temperature range 1180-1353 K was investigated by employing a thermogravimetric analysis system, an X-ray diffractometer, a scanning electron microscope and a surface area analyzer. Experimental results indicated that calcium carbonate decomposed almost completely in 210 s under 1303 K. Shape and size of a CaCO3 grain did not change during decomposition. Specific surface area and specific pore volume increased while pore diameter was unchanged after decomposition. The apparent activation energy was found to be 84.89 kJ/mol.