To provide a boiler device capable of keeping the inlet gas temperature of a denitration device constant regardless of a variation in a boiler load.

This boiler device is characterized by individually arranging dampers 7 and 22 for adjusting a gas flow rate on the downstream side of a first economizer 24 and a second economizer 23, by arranging the first economizer 24 constituted of a first heat transfer tube much in a hear absorption quantity per the unit length and the second economizer 23 constituted of a second heat transfer tube little in the heat absorption quantity per the unit length, in the direction crossing with the flowing direction of exhaust gas, in a rear flue part 1.