Abstract : Recent experiments of neutrino-less double beta decays have been developing for studying the effective mass of neutrinos. Some of them use plastic scintillator for detecting the beta ray energy. Good energy resolution is a key for the neutrino- less double beta decay experiments (MOON, superNEMO, etc.). The motivation in this work is to study the energy resolution of a plastic scintillation counter in terms of "components" in the MeV-electron region. It is known that total energy resolution of a scintillation counter for a mono-energetic spectrum is separated into two components (statistical and non-statistical components). This paper presents for studying these two components on a plastic scintillation counter for electrons. Experiments on protons are also performed to compare to electron data. Experimental results point out that the statistical component is inversely proportional to the square root of the number of photo-electrons. In the case of electrons, data set of the non-statistical component described as approximately inversely proportional to the square root of electron energies. Three additional experiments are needed to carry out, (such as measuring (1) the uniformity of the plastic scintillator materials, BC-408, by scanning a 2.8-MeV proton micro-beam, (2) the energy spread of electrons and protons, and (3) the effect of electron-beam size on the set-up), to be sure that they do not affect measuring these two components. This present work is useful for investigating as well as improving the energy resolution of a plastic scintillation counter through statistical and non-statistical components.