  We study mirror symmetry of Calabi-Yau manifolds within the framework of the
Gauss-Manin system. Applying the flat coordinates to the Gauss-Manin system for
the periods, we derive differential equations for the mirror map in addition to
the ordinary Picard-Fuchs equations for the periods. These equations are
obtained for a class of one-parameter models and a two-parameter model of
Fermat type Calabi-Yau manifolds.
