PURPOSE: To judge beforehand the necessity of disassembling and inspecting a valve by selecting a valve, the driving mechanism of which is deteriorated among a lot of electrically operated valves.

CONSTITUTION: An input voltage and an input current of a valve driving electric motor 1 are input to a converter 14 through an instrument transformer 2 and a current transformer 3, and the voltage, current and power factor are converted to digital values by the converter 4 to be input to a central processing unit 5. In the processing unit 5, the input electric energy of the valve driving electric motor is calculated from the input and transmitted and stored as a series of data together with inputs from a keyboard 6 in an auxiliary memory device 7. The initial data is obtained by conducting the above operation when a valve is sound, and after the lapse of a fixed period, a series of operations are performed to the compared with the initial data. Thus, the deterioration of an electrically driven valve is judged.