  We study the Picard-Fuchs differential equations for the Seiberg-Witten
period integrals in N=2 supersymmetric Yang-Mills theory. For A-D-E gauge
groups we derive the Picard-Fuchs equations by using the flat coordinates in
the A-D-E singularity theory. We then find that these are equivalent to the
Gauss-Manin system for two-dimensional A-D-E topological Landau-Ginzburg models
and the scaling relation for the Seiberg-Witten differential. This suggests an
interesting relationship between four-dimensional N=2 gauge theories in the
Coulomb branch and two-dimensional topological field theories.
