To provide a corrosion prevention method of a boiler with which a corrosion prevention effect and scale prevention effect of copper can be simultaneously obtained in a boiler water system containing copper in feed water.

The corrosion prevention method of the boiler containing the copper in the feed water comprises adding a rust preventive material to the boiler water system in such a manner that the oxidation-reduction potential of blow water turns to 0 mV. An anticorrosive material has low deoxidizing capability and for example, a succinic acid or its salt, citric acid or its salt, a sorbic acid or its salt can be used.