  It is shown that softly broken theory is equivalent to a rigid theory in
external spurion superfield. The singular part of effective action in a broken
theory follows from a rigid one by a simple redefinition of the couplings. This
gives an explicit relation between the soft and rigid couplings
renormalizations. As an illustration the renormalization group functions in the
MSSM have been calculated. The method opens a possibility to construct a
totally all loop finite N=1 SUSY gauge theory, including the soft SUSY breaking
terms. Explicit relations between the soft terms, which lead to a completely
finite theory in any loop order, are given.
