PURPOSE: To aurally notify that a piezoelectric element constituting a fine moving mechanism comes into contact with another mechanism when the piezoelectric element is moved or stopped or to stop automatically a change caused by the piezoelectric element or moving mechanism by detecting an AC component generated when the piezoelectric element comes into contact with another mechanism.

CONSTITUTION: A contact detector is constituted of a piezoelectric element 2 which is finely moved by applying a voltage across the element 2, voltage control section 4 which finely moves the element 2 by applying the voltage, current detecting resistor 5 which detects the electric current flowing to the element 2, and filter which extracts an AC component from a signal detected by means of the resistor 5 so that the detector can output the AC component extracted by means of the filter 6 as sounds after amplification.