The present invention relates to a high-output diamond semiconductor element, including a Schottky electrode as a cathode, a diamond P− drift layer, a diamond p+ ohmic layer, an ohmic electrode as an anode, and an insulating film layer disposed to surround a circumference of the Schottky electrode. It also relates to a high-output diamond semiconductor element, including a Schottky electrode as a cathode, a diamond P− drift layer, a diamond p+ ohmic layer, an ohmic electrode as an anode, a dielectric layer disposed on a part of a junction surface of the Schottky electrode and the diamond p− drift layer, and a field plate containing a conductor, the field plate being disposed on an external surface of the dielectric layer to surround a circumference of the Schottky electrode.