A vibration detecting apparatus comprises a housing having at one end thereof an opening, a piezoelectric element disposed within the housing, a connector mounted to the housing to cover the opening thereof and having an output pin, a lead wire for electrically connecting the piezoelectric element with the output pin, and an initially conical annular spring having an outer peripheral edge portion thereof received by an annular groove formed in an inner peripheral wall of the housing. The piezoelectric element is biased by the initially conical annular spring.