  The normal muon decay $\mu^{+} \to e^{+}\nu_{e}\bar{\nu_{\mu}}$ is studied as
a tool to discriminate between the Dirac and Majorana type neutrinos. For the
purpose to do this, we propose a new parameterization in place of the Michel
parameters for the energy spectrum of $e^{+}$. The $\chi^2$-fitting is used by
noticing different energy spectra between the Dirac and Majorana neutrino
cases. We assume the interaction Hamiltonian which consists of the $V-A$ and
$V+A$ charged currents.
