PURPOSE: To obtain the two-freedom degree controller whose target follow-up responsiveness is satisfactory.

CONSTITUTION: The device is provided with a feedback controller design means 2 for designing a feedback controller corresponding to a control objct by a prescribed method, a mode decomposing means 4 for decomposing the feedback controller to modes, and a controller fundamental structure determining means 6 for determining a fundamental structure as a difference of that which is obtained by multiplying a target input by feedforward constant gain corresponding to each mode at every mode, based on the feedback controller subjected to mode decomposition, and that which is obtained by multiplying an observation output of the control object becomes an input of the corresponding mode, and by adding outputs of each mode, its sum becomes a control input.