By applying a drive voltage Vf [V] between first and second conductive films, when electrons are emitted by the first conductive film, an equipotential line of 0.5 Vf [V] is inclined toward the first conductive film, rather than toward the second conductive film, in the vicinity of the electron emitting portion of the first conductive film, in a cross section extending across the electron emitting portion and the portion of the second conductive film located nearest the electron emitting portion. The present invention improves electron emission efficiency.