  We report the study of spontaneous magnetization (i.e., spin-polarization)
for time-reversal symmetry (TRS)-breaking superconductors with unitary pairing
potentials, in the absence of external magnetic fields or Zeeman fields.
Spin-singlet ($\Delta_s$) and spin-triplet ($\Delta_t$) pairings can coexist in
superconductors whose crystal structure lacks inversion symmetry. The TRS can
be spontaneously broken once a relative phase of $\pm\pi/2$ is developed,
forming a TRS-breaking unitary pairing state ($\Delta_s\pm i\Delta_t$). We
demonstrate that such unitary pairing could give rise to spontaneous
spin-polarization with the help of spin-orbit coupling. Our result provides an
alternative explanation to the TRS breaking, beyond the current understanding
of such phenomena in the noncentrosymmetric superconductors. The experimental
results of Zr$_3$Ir and CaPtAs are also discussed in the view of our theory.
