To provide an electron emission element attaining stable electron emission both in a vacuum and the atmosphere and suppressing generation of harmful substances such as ozone and NOx incidental to electron emission.

The electron emission element 1' has an electron accelerating layer 4' between a substrate 28 and an upper electrode 3. The electron accelerating layer 4' contains highly anti-oxidative metal fine grains 6 and an insulator substance 5' larger than the metal fine grain in grain size. The insulator substance 5' is layered on a substrate and has a plurality of openings 51 formed to pass through the thickness of the layer. The metal fine grains 6 are contained in the openings 51. The electron emission element 1' emits electrons stably both in a vacuum and the atmosphere, discharges no electricity and hence hardly generates the harmful substances such as ozone and NOx and is free from oxidative deterioration. Thus, the electron emission element 1' has a long service life and achieves stable, long-lasting and continuous operation even in the atmosphere.