  We obtain the exact beta function for $N=2$ SUSY $SU(2)$ Yang-Mills theory
and prove the nonperturbative Renormalization Group Equation $$
\partial_\Lambda{\cal F}(a,\Lambda)= {\Lambda\over
\Lambda_0}\partial_{\Lambda_0}{\cal F}(a_0,\Lambda_0) e^{-2\int_{\tau_0}^\tau
{dx \beta^{-1}(x)}}. $$
