  We apply tilting theory over preprojective algebras $Lambda$ to a study of
moduli space of $Lambda$-modules. We define the categories of semistable
modules and give an equivalence, so-called reflection functors, between them by
using tilting modules over $Lambda$. Moreover we prove that the equivalence
induces an isomorphism of algebraic varieties between moduli spaces. In
particular, we study in the case when the moduli spaces related to the Kleinian
singularity. We generalize a result of Crawley-Boevey which is known another
proof of the McKay correspondence of Ito-Nakamura type.
