The formaldehyde is damage to the metal are known universally. However, the quantification of the damage level and degree of damage is not clear. This study was conducted to test the following steps using a gas corrosion tester, and then evaluated by the optical, chemical and physical measurement. First, it was confirmed the damage level of the metal specimen(silver, copper, iron, lead, brass) by the formaldehyde(0.5, 1, 10, 100, 500 ppm). Second, Weighted damage to the metal specimens were tested according to the temperature and humidity conditions under damage levels. Third, the damage of accelerated degradation metal specimens were examined under damage levles. As a result, At 500 ppm / day, the optical, chemical and physical damage of lead have been identified, the optical damage of all metals are was observed. the optical damage of some specimens were weighted in 25℃-50%, 30℃-50%. Chemical damage to the lead specimen is 2.8 times, 1.3 times were weighted in 30℃-80%, 25℃-80%. Referring to formate ion concentration of the accelerated degradation metal, corrosion products of iron and brass were actived the reaction of the formaldehyde gas, oxide film of lead was blocked the reaction of formaldehyde gas.