In the shemes of Migdal and Migdal-Kadanoff renormalization group transformation, the strong coupling (high temperature) approximation and weak coupling (low temperature) approximation for U(l) lattice gauge theory are introduced, and the numerical results, including those for the intermediat coupling region, are given. We compare the results obtained by means of these transfomations with the exact results of strong coupling and weak coupling expansions and the recent Monte-Carlo calculation.