A wiring board includes a first conductor formation substrate having a first substrate and a first electrode; a second conductor formation substrate having a second substrate and a second electrode; and a dielectric sandwiched between the first conductor formation substrate and the second conductor formation substrate. The dielectric includes a dielectric film that is not melted during thermo-compression bonding, and an adherent insulator melted during thermo-compression bonding. The surface of the dielectric film is subjected to a treatment to improve wettability. Adherence of the adherent insulator in thermo-compression bonding to the dielectric film is facilitated. The distance between the first electrode and the second electrode is made uniform by interposing the dielectric film between the first and second electrodes. A wiring board ensured as to lifetime and improved in reliability, and a simple method of fabricating such a wiring board are achieved.