  We study Baxter's T-Q equation of XXX spin-chain models under the
semiclassical limit where an intriguing SU(N)/SU(2)^{N-3} correspondence
emerges. That is, two kinds of 4D \mathcal{N}=2 superconformal field theories
having the above different gauge groups are encoded simultaneously in one
Baxter's T-Q equation which captures their spectral curves. For example, while
one is SU(N_c) with N_f=2N_c flavors the other turns out to be SU(2)^{N_c-3}
with N_c hyper-multiplets (N_c > 3). It is seen that the corresponding
Seiberg-Witten differential supports our proposal.
