  On the evaluation of $\tan{\beta}$ is revisited by the method of the
renormalization group with the criteria of the bottom-tau unification in the
SUSY SU(5) GUT model. Among the conventional supersymmetric theories, an
energy-scale constant $M_{SUSY}$ is introduced by-hand to decouple the lower
energy-scale region from the effects of the supersymmetric particles. Provided
that $M_{SUSY}$ really exists, only small $\tan{\beta} \simeq 2$ is allowed
theoretically. While, medium value as $\tan{\beta} = 6 \sim 25$ is also
supported if $M_{SUSY}$ is vanished away from the model.
