To reduce the number of workers and transceivers in the case of performing a loop check.

A liquid crystal display part 7G is provided in an electropneumatic positioner 7. A flow value Qpv from a flow meter 4 is fed to the electropneumatic positioner 7. The liquid crystal display part 7G is formed so that it can selectively display the flow value Qpv from the flow meter 4, an actual opening 0pv from a regulating valve 3 and an internal temperature tpv. By this way, in the case of performing a loop check, it is only required that workers A, B are respectively arranged in a side of a host supervisory system 1 and the regulating valve 3 to make the worker A carry a transceiver 5-1 and the worker B carry a transceiver 5-2. That is, by eliminating necessity for stationing a worker in a side of the flow meter 4, even necessity for using two sets of the transceivers is eliminated.