PURPOSE: To adjust parameters of the PID controller by finding optimum parameters in a short time in the state of a closed loop system wherein the PID controller is connected.

CONSTITUTION: The PID controller 1 which performs three proportional, integral, and derivative operations is arranged in a feedback loop, and the parameter adjustment device 100 calculates the manipulated variable of a process 2 on the basis of a command (r), a controlled variable (y), and a control deviation (e). An identification part 10 approximates the process 2 with an autoregressive movement mean model in the structure of an equation 'yk=akk-1+b1uuk+ b2uk-1+c1dk-1+c2dk-2c3' (where (y) is the controlled variable, (u) a manipulated variable, (d) known disturbance, and (a), (b), and (c) parameters), and identifies the idle time L, gain λ, time constant τ1 of first order delay characteristics, and constant τ2 of first order leading characteristics by a method of the least squares. An adjusted parameter setting part 11 calculates parameters Kp, Rs, and Td from the values L, λ, τ1, and τ2 obtained by the identification and displays them at a display part 12.