In general, it is known that the blast-furnace slag cement has more small resistance for carbonation compared with ordinary Portland cement. However, that the wonder is that universal? According to resent research, as a result of investigating the actual structures that it was built using ordinary Portland cement and blast-furnace slag cement, carbonation depth was similar in concrete using each cement. However, the result of accelerated carbonation test using these concrete cores, the carbonation depth of blast-furnace slag cement is increased significantly. This is a great property of blast-furnace slag cement. According to these results, it is affected by moisture into concrete. However, the mechanism of carbonation progress on using different cement types would be not same on different situation such as different concentration of carbon dioxide. Therefore it is considered possible to clear the mechanism is important scientifically.