The present invention prevents occurrence of electrical discharge on an electrically conductive structure in an environment in which high-energy electrons impinge onto the structure or on an electronic element mounted to a surface of the structure, which electrical discharge would otherwise occur when the potential of the structure or the electronic element increases in the negative direction due to a negative charge flowing thereinto. An insulating tape bonded to the surface of the electrically conductive structure is partially cut-removed; an electrically conductive adhesive is applied to an exposed portion of the surface of the electrically conductive structure; and an insulating film is bonded to the electrically conductive adhesive, such that the electrically conductive adhesive is exposed to the outside. When encountering higher-energy electrons, the insulating film is charged, so that a strong electric field is applied to the electrically conductive adhesive, and electrons are emitted from the electrically conductive adhesive through field electron emission, to thereby prevent the potential of the electrically conductive structure from increasing in the negative direction.