PURPOSE: To embody a device which easily adjusts the proportional gain and the integral gain.

CONSTITUTION: The PI controller provided with first and second constant multipliers 3 and 4 to which the deviation between a target value 1 and a process value 11 is inputted, an integrator 8 to which the output signal or the second constant multiplier 4 is inputted, and an adder 9 which takes output signals or the first constant multiplier 3 ana the integrator 8 as inputs and inputs the output signal to a control object 10 is provided with a third constant multiplier 5 to which the deviation is inputted, a differentiator 6 to which the output signal of this multiplier 5 is inputted, and a subtractor 7 which is provided between the second constant multiplier 4 and the integrator 8 and subtracts the output signal or the differentiator 6 from that of the second constant multiplier 4, and thereby, hunting is suppressed by correction based on the differential signal even in the case of a high integral gain because the gain adjustment is facilitated, thus quickly following the target value and sufficiently following the quick change of the target value.