PURPOSE: To provide a boiler control device capable of performing a high performance operation of a boiler without being influenced against a surface moisture amount of coal applied.

CONSTITUTION: There are provided a heat balance calculation device 26 in which a mill outlet air temperature 21s, an inlet air temperature 22s, an inlet air volume 23s, a coal feeding amount 24s, a power 25s and a coal specific moisture 26s are inputted and then a surface moisture signal for coal is outputted under a heat balance, and a coal calorific value calculation device 27 in which an output from the heat balance calculation device 26 and a coal specific moisture signal are inputted and a coal calorific value signal is outputted. In addition, as front stage of a boiler control device 30 there are provided a fuel flow rate correction calculation device 28 which receiving an output of the coal calorific value calculation device 27 outputs a fuel flow rate correcting signal, and an economizer necessary gas bypassing amount discriminating device 29 which receiving an output from the heat balance calculation device 26 outputs a bypass signal when the input is more than a predetermined value.