To provide a thermion source which is applied in a display device having high current density and high brightness, a logical circuit, and other heat power source field or the like, and has superior performance in thermion emission and a long service life.

This thermion source includes a substrate, at least two electrodes, and a thermion emission element. The thermion emission element is electrically connected at least to two electrodes, includes a carbon nanotube structural body, and is installed separatedly from the substrate.