The High-Energy Particle Detector (HEPD) is one of the payloads of the CSES space mission, built by the Italian “Limadou” collaboration. It will study the temporal stability of the inner Van Allen radiation belts, the precipitation of trapped particles in the atmosphere and the low energy component of the cosmic rays (5 - 100 MeV for electrons and 15 - 300 MeV for protons). Results of the test beams held at the Beam Test Facility of the INFN National Laboratory of Frascati, for electrons, and at the Proton Cyclotron of Trento, for protons, will be presented. The performance of the apparatus both on the energy reconstruction and in the lepton/hadron separation will be shown.