The present invention relates to a conductor having high conductivity and electrochemical stability, which is in a solid state over a practically wide temperature range. Specifically disclosed is a plastic crystal containing a compound represented by Formula (I) or (IA) below: and at least one compound [BF3(CF3)] salt represented by Formula (II): Mn+[BF3(CF3)−]n  (II) wherein M is an alkaline metal, alkaline earth metal, aluminum or H; and when M is an alkaline metal or H, n is 1; when M is an alkaline earth metal, n is 2; and when M is aluminum, n is 3.