To provide a means capable of easily determining an operation state of a valve element of an electromagnetic control valve without increasing cost.
In a method of detecting an operation state of the electromagnetic control valve opening/closing the valve element by exciting a solenoid coil by a power current, leakage flux (m) generated around the solenoid coil 12 is detected by a leakage flux detection coil 21 set in the vicinity of the solenoid coil 12; variation of the leakage flux is treated as voltage waveform; and the voltage waveform is compared with the voltage waveform when the valve element 14 normally operates and the voltage waveform when the valve element does not normally operate, whereby the operation state of the electromagnetic valve 7 is determined.
Hiroshi Matsumoto