  We study a particle production at the collision of two domain walls in
5-dimensional Minkowski spacetime. This may provide the reheating mechanism of
an ekpyrotic (or cyclic) brane universe, in which two BPS branes collide and
evolve into a hot big bang universe. We evaluate a production rate of particles
confined to the domain wall. The energy density of created particles is given
as $\rho \approx 20 \bar{g}^4 N_b ~m_\eta^4 $ where $\bar{g}$ is a coupling
constant of particles to a domain-wall scalar field, $N_b $ is the number of
bounces at the collision and $m_\eta$ is a fundamental mass scale of the domain
wall. It does not depend on the width $d$ of the domain wall, although the
typical energy scale of created particles is given by $\omega\sim 1/d$. The
reheating temperature is evaluated as $T_{\rm R}\approx 0.88 ~ \bar{g} ~
N_b^{1/4}$. In order to have the baryogenesis at the electro-weak energy scale,
the fundamental mass scale is constrained as $m_\eta \gsim 1.1\times 10^7$ GeV
for $\bar{g}\sim 10^{-5}$.
