  We define motivic Milnor fiber of cyclic $L_\infty$-algebras of dimension
three using the method of Denef and Loeser of motivic integration. It is proved
by Nicaise and Sebag that the topological Euler characteristic of the motivic
Milnor fiber is equal to the Euler characteristic of the \'{e}tale cohomology
of the analytic Milnor fiber. We prove that the value of Behrend function on
the germ moduli space determined by $L$ is equal to the Euler characteristic of
the analytic Milnor fiber. Thus we prove that Behrend function depends only on
the formal neighborhood of the moduli space.
