  Nodal-line semimetals with magnetic orders have been theoretically predicted
and experimentally observed in only few compounds. We theoretically explore the
electronic structure in bulk and boundary of such a magnetic nodal-line state
by introducing magnetism in topological Dirac semimetal (TDSM). TDSMs, such as
$\mathrm{Cd_3 As_2}$ and $\mathrm{Na_3 Bi}$, are characterized by a pair of
spin-degenerate Dirac points protected by rotational symmetries of crystals. By
introducing local magnetic moments coupled to the electron spins in the lattice
model of TDSM, we show that the TDSM can turn into either a Weyl semimetal or a
nodal-line semimetal, which is determined by the orbital dependence in the
exchange coupling and the direction of magnetization formed by the magnetic
moments. In this magnetic nodal-line semimetal state, we find zero modes with
drumhead-like band structure at the boundary that are characterized by the
topological number of $\mathbb{Z}$. Those zero modes are numerically
demonstrated by introducing magnetic domain walls in the lattice model.
