An evaporation technique with high thermal efficiency in an electron beam evaporation process is presented for the generation of copper vapor. A molybdenum hearth Liner and a porous rod made of sintered tungsten with evaporation material were set into a bare water-cooled copper crucible. While the top surface of the porous rod was heated by an electron beam, the molten copper surrounding the rod is transferred to the top surface of the rod through pores in the rod by capillarity and then copper vapor stream was generated from there. The evaporation characteristics were measured with a quartz crystal sensor, a charge coupled device camera, deposited weights, and a quadrupole mass spectrometer. An extremely high vapor flux with high stability was obtained for a long period of time even at low input power without contamination by tungsten atoms which are porous materials and also without the formation of the dimers.