To speedily and efficiently tune a prescribed corresponding relation by evaluating the probability of an output variable estimated based on estimation parameters before and after a change, selecting the optimum estimation parameter whose evaluation is the highest and controlling the prescribed corresponding relation.

An estimation parameter change block 26B generates one new individual. Evaluation values as the indexes of the probability of estimation values Vyhat are operated on the respective individuals based on the measured value of relative speed and the estimated value Vyhat of relative speed between a space above a spring and a space below the spring when an attenuation force controller 10 tries the control of a shock absorber 16 based on gene information of the respective individuals of a new generation containing the new individual. Furthermore, an estimation parameter selection block 26C erases the individual whose evaluation value is the lowest and selects the individual whose evaluation value is the highest. An adjustment block 26D outputs the combination of the optimum parameters to an observer 12.