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 ate obtained for a class of one-parameter mo
dels and a two-parameter model of Fermat type Calabi-Yau manifolds.