To provide an electron emission element, an electron source, an electron beam device, and a manufacturing method for the electron emission element capable of obtaining a sufficient amount of emitted electrons and making a thin diameter of an electron beam.

In the electron source 10, electron affinity and a work function of an electron emission section 48 can be sufficiently reduced since a projection section 56 made of a n-type diamond semiconductor as a conductive type is arranged on the electron emission section 48, and a sufficient amount of emitted electrons can be obtained. A thinner diameter of the electron emission section 48 is achieved so that the thinner diameter of the electron beam emitted from the electron emission section 48 can be carried out without applying complicated processing on the projection section 56 by preparing the fine projection section 56 conveyed by a micro manipulation. Firm connection between the projection section 56 and a base section 52 can be maintained since a deposition film 60 is formed by carbon and the deposition film 60 has a sufficiently high melting point against temperature rise of the electron emission section 48 at a used state of the electron source 10.