Recently, it has been a problem that ant's nest corrosion occur in phosphorus deoxidized copper (hereinafter called PDC) tubes for indoor equipment in room air-conditioner. We've developed zinc plating copper tube on sacrificial anticorrosion effect to ant's nest corrosion. The corrosion resistance of the tube was evaluated compared with corrosion properties of PDC and oxygen free copper (hereinafter called OFC) by vapor phase exposure test in a sealed container having a corrosive medium of 100 mg/L formic acid solution. In addition, it was also evaluated corrosive properties of OFC. Zinc plating copper tube has been completely suppressed ant's nest corrosion during corrosion test. We considered that OFC has slow corrosion property in the depth direction, because corrosion source part at bottom of corrosion hole in OFC is less than in PDC.