To provide a boiler controller having a quick response to the change of load immediately after the start of operation without the need of a accumulating operation data.

In this controller, a plurality of discrete value 51 and the setting value of a controlled variable 52 are input to an adder 53 and deviation is acquired, the control error 61 output from the adder 53 is accumulated by a accumulating compensator 54, the accumulated value 62 is input to a control gain matrix K1 (55) on the side of the discrete value and output as a manipulated variable m. A manipulated variable 59 to a boiler B output from the adder 56 is input also to a boiler dynamic characteristic model 57 for acquiring the estimated value of the inner state 63 of the boiler, such as the inlet and outlet steam temperature, pressure and enthalpy of each heat transferring element, and the estimated value of the inner state 63 estimated by the boiler dynamic characteristic model 57 is input into the control gain matrix K2 (58) and output as a manipulated value n. A final manipulated variable 59 is output as the added value of the manipulated variable m that is the calculated value of the control gain matrix K1 (55) and the manipulated variable n that is the calculated value of a control gain matrix K2 (58).