  The antiferromagnetic (AFM) order in the Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) superconducting state is analyzed on the basis of a Ginzburg-Landau
theory. To examine the possible AFM-FFLO state in CeCoIn_5, we focus on the
incommensurate AFM order characterized by the wave vector Q = Q_{0} \pm q_inc
with Q_0 =(\pi,\pi,\pi) and q_inc \parallel [110] or [1-10] in the tetragonal
crystal structure. We formulate the two component Ginzburg-Landau theory and
investigate the two degenerate incommensurate AFM order. We show that the
pinning of AFM moment due to the FFLO nodal planes leads to multiple phases in
magnetic fields along [100] or [010]. The phase diagrams for various coupling
constants between the two order parameters are shown for the comparison with
CeCoIn_5. Experimental results of the NMR and neutron scattering measurements
are discussed.
