To provide a new valve element detecting method of a valve capable of easily distinguish the presence of collision of a valve element with a cage without disasembling.

Acceleration of a valve stick 6 connected to a valve element 4 of a valve is measured to obtain Fourier spectrum by processing the wave form of the acceleration by means of fast Fourier transformation. On the other hand, an analytical model is formed in relation to the valve element 4, the valve stick 6 and a cage 5. Sinusoidal wave of frequency is given to the analytical model, wave form of response acceleration of a modelling part of the valve stick 6 is outputted by analyzation in relation to time hystory, and the wave form of response acceleration is processed by means of fast Fourier transformation to obtain Fourier spectrum the same as the valve. Comparison of the Fourier spectrum of the valve and the analytical model is used to distinguish the presence of collision of the valve element 4 and the size of clearance.