PURPOSE: To improve controllability of a feedback controller.

CONSTITUTION: A control output y(n) of a controlled system 2 is fed back to an adjusting part 8 by switching changeover switches 5 and 6 and a control input u(n), control output y(n) and differentiated value dy(n) are time sequentially stored in a memory 3. A state prediction part 7 predicats a control output y(t+L) at certain time after the lapse of dead time L based on the control output y(t) at time (t) stored in the memory 3 or the like. Weighting at the state prediction part 7 is adjusted so as to minimize error between this control output and a control output y*(t+L) at the same time stored in the memory 3. By switching the changeover switches 5 and 6, the state prediction part 7 predicts a control output y(n+L) at certain time after the lapse of the dead time L by applying the weight adjusted to the present control output y(n) or the like, and this predicted control output y(n+L) is fed back to the adjusting part 8.