  We discuss a possibility of the presence of a stable color ferromagnetic
state in SU(2) gauge theory of quark matter; a color magnetic field is
spontaneously generated due tothe gluon's dynamics. The state arises between
the hadronic state and the color superconducting state when the density of
quarks is varied. Although the state has been known to have unstable modes, we
show that unstable modes form quantum Hall states, in which the instability
disappears. Namely, the quark matter possesses a stable phase with the
ferromagnetic state and the quantum Hall state of gluons.
