  Particle acceleration in the magnetic reconnection of electron-positron
plasmas is studied by using a particle-in-cell simulation. It is found that a
significantly large number of nonthermal particles are generated by the
inductive electric fields around an X-type neutral line when the reconnection
outflow velocity, which is known to be an Alfv\'{e}n velocity, is on the order
of the speed of light. In such a relativistic reconnection regime, we also find
that electrons and positrons form a power-law-like energy distribution through
their drift along the reconnection electric field under the relativistic
Speiser motion. A brief discussion of the relevance of these results to the
current sheet structure, which has an antiparallel magnetic field in
astrophysical sources of synchrotron radiation, is presented.
