Provided are an electron multiplier electrode using a secondary electron extraction electrode and a terahertz radiation source using the electron multiplier electrode. The electron multiplier electrode includes: a cathode; an emitter disposed on the cathode and extracting electron beams; a gate electrode for switching the electron beams, the gate electrode being disposed on the cathode to surround the emitter; and a secondary electron extraction electrode disposed on the gate electrode and including a secondary electron extraction layer extracting secondary electrons due to collision of the electron beams.