  Recent results on the mixing-induced CP asymmetries of B \to \phi K^0 and B
\to \eta' K_S measured at B-factories appear to indicate discrepancies from the
Standard Model expectation. Explanation of this possible anomaly is given in
the context of supersymmetric extension of the Standard Model. It is shown that
the present data, if the average of two experiments is taken, implies
additional CP violation appearing in the generation mixing of left-handed
squarks rather than that of right-handed ones. This explanation is argued to
disfavor many mediation mechanisms of supersymmetry breaking, including minimal
supergravity, because renormalization group effects via Yukawa interaction are
unlikely to generate the desired mass mixing.
