  We study the equation of state of electron in strong magnetic fields which
are greater than the critical value $B_c \simeq 4.4 \times 10^{13}$ Gauss. We
find that such a strong magnetic field induces the anisotropic pressure of
electron. We apply the result to the neutrino-driven wind in core-collapse
supernovae and find that it can produce large entropy per baryon, $S \sim 400
k_B$. This mechanism might successfully account for the production of the heavy
nuclei with mass numbers A = 80 -- 250 through the r-process nucleosynthesis.
