A functional molecular device displaying its functions under the action of an electrical field is provided. A Louis base molecule, exhibiting positive dielectric constant anisotropy or exhibiting dipole moment along the long-axis direction of the Louis base molecule, is arrayed in the form of a pendant on an electrically conductive linear or film-shaped principal-axis molecule of a conjugated system, via a metal ion capable of acting as a Louis acid. The resulting structure is changed in conformation on application of an electrical field to exhibit its function. The electrically conductive linear or film-shaped principal-axis molecule and the Louis base molecule form a complex with the metal ion. On application of the electrical field, the Louis base molecule performs a swinging movement or a seesaw movement to switch the electrical conductivity of the principal-axis molecule. This molecule exhibits electrical characteristics which may be reversed depending on whether or not the molecule has been subjected to electrical field processing. A molecular device having a function equivalent to one of CMOS may be produced from one and the same material.