PURPOSE: To prevent deterioration in responsiveness and stability to be caused by disturbance or the like in a control device such as an actuator in a fluid motor, by adding deviation between a target position signal and a position sensor signal to deviation between a model speed signal and a speed signal, while controlling a control valve.

CONSTITUTION: Position and speed of a cylinder 11 is respectively detected by sensors 15, 16. Deviation between a target position signal and an output of the position sensor 15 is calculated by a first subtraction circuit 17 and input into a compensation circuit 18. From the signal of the compensation circuit 18, a value of the speed sensor 16 corresponding to the output of the first subtraction circuit 17 by a model signal generation means 21, and a deviation in respect to the signal of the speed sensor 16 is calculated by a second subtraction circuit 22. The deviation is added to the output of the compensation circuit 18 in an addition circuit 25 through a reverse model signal generation means 23. A control valve is controlled through a driver 13, and a cylinder 11 is driven. Inertia load, change of friction coefficient, and disturbance are compensated, and control is carried out without deteriorating responsiveness and stability.