PURPOSE: To suppress the influence of the vibration of a piping system to improve the vibrationproofness by feedback-supplying the electric signal which is obtained by the conversion of the displacement quantity of the working shaft of a driving device which is arranged separately from a positioner to a control calculation part, and transmitting the difference between this signal and the input to the positioner to an electricity-air conversion part.

CONSTITUTION: The displacement of a working shaft which is detected mechanically is converted to the electric signal by a displacement detection part 31 and inputted into an A/D conversion part 46, together with the signal of an input electric current detection part 45 for detecting the input signal to a valve positioner, and inputted as the A/D converted feedback signal into a control calculation part 47. Further, an electricity-air conversion part 48 is constituted of a magnet unit, nozzle flapper mechanism, and a pilot relay, and when the input signal is varied according to a set value, and a difference from a displacement detection part 31 is generated, the correction signal of the control calculation part 47 is received to drive a driving device 3. Accordingly, the need of directly installing the positioner to the driving device 3 is obviated, and the influence of the vibration of a piping system is suppressed, the vibrationproofness is improved, and the installation work and adjusting work can be carried out easily in simple manners.