  A relation between nuclear forces derived using a phenomenological approach
and nuclear effective field theory (NEFT) is proposed from a renormalization
group point of view. A phenomenological nuclear force (V_ph) and an NEFT-based
NN-potential (V_EFT) are satisfactorily related to each other through the
Wilsonian renormalization group (WRG) method. It is clearly shown that use of
the simple contact interactions in NEFT is adequate to simulate small scale
phenomena, and that an NEFT-based NN-potential (V_EFT) is free from dependence
on the model used to describe small scale phenomena. We study the
characteristics of V_EFT from a WRG point of view, emphasizing points that have
not previously been fully recognized. We also use the V_{low k} method and a
unitary transformation method to relate V_ph to V_EFT. It is found that they
are not appropriate for this purpose.
