An external operation detection structure body including: a sensor casing having an aperture window; an external operation detection sensor arranged at a formation zone of the aperture window; a sheet-like interface member that covers a front face of the detection sensor and closes the aperture window; an outer peripheral wall protruding out from a rear face of an outer periphery of the interface member and penetrating into the aperture window so as to be arranged between the detection sensor and the sensor casing; and front and rear face seal protrusions extending respectively from front and rear edges of the outer peripheral wall toward an outer peripheral side so as to be superposed respectively with front and rear faces of a peripheral edge of the aperture window of the sensor casing.