Abstract: The present invention provides an electron emitting device for efficiently emitting electron beams by applying a forward bias to an MIS, pn, and a pin structure using a diamond layer so as to supply electrons from an electron supply layer to a p-type diamond layer. Furthermore, the present invention provides a method for easily and efficiently performing important production processes for producing a highly efficient electron emitting device having a diamond layer and controlling a surface state of the diamond layer. A multi-layer structure including an electrode layer, an electron supply layer and a diamond layer is used as the structure thereof. Alternatively, the electron affinity state of the surface of the diamond layer is arbitrarily controlled by a method such as ultraviolet ray irradiation.