  A mechanism of supersymmetry breaking in two or four-dimensions is given, in
which the breaking is related to the Fermat's last theorem. It is shown that
supersymmetry is exact at some irrational number points in parameter space,
while it is broken at all rational number points except for the origin.
Accordingly, supersymmetry is exact {\it almost everywhere}, as well as broken
{\it almost everywhere} on the real axis in the parameter space at the same
time. This is the first explicit mechanism of supersymmetry breaking with an
arbitrarily small change of parameters around any exact supersymmetric model,
which is possibly useful for realistically small non-perturbative supersymmetry
breakings in superstring model building. As a byproduct, we also give a
convenient superpotential for supersymmetry breaking only for irrational number
parameters. Our superpotential can be added as a ``hidden'' sector to other
useful supersymmetric models.
