The objective of the present study is to analyze separation capability of charged particles of small-scale cusp type direct energy experimental converter installed at GAMMA 10 by means of numerical simulation with the axisymmetrical two-dimensional approximation. The numerical simulation has given the following results: (1) when the input power of protons is less than or equal to 1W, the protons and the electrons can be separated with the proton collection efficiency of 100%. When the input power of protons is 5W, the protons and the electrons become difficult to be separated with the proton collection efficiency of about 5%. (2) The electrons whose radius of incidence is small become trapped in the separation zone. These results depend on the magnitude of self-induced electric field which is formed by separation of the protons and the electrons.