  We discuss the stochastic process of creation and annihilation of particles,
i.e., the $A^{n} \rightleftarrows B$ process in which $n$ particles $A$s and
one particle $B$ are transformed to each other. Considering the case that the
stochastic fluctuations are dependent on the numbers of $A$ and $B$, we apply
the Langevin equation for the stochastic time-evolution of the numbers of $A$
and $B$. We analyze the Langevin equation in the path-integral formalism, and
show that the new driving force is generated dynamically by the stochastic
fluctuations. We present that the generated driving force leads to the
nontrivial stable equilibrium state. This equilibrium state is regarded as the
new state of order which is induced effectively by stochastic fluctuations. We
also discuss that the formation of such equilibrium state requires at least two
stochastic variables in the stochastic processes.
