  We study the change of the effect of the current quark mass on the
inhomogeneous chiral phase in the QCD phase diagram, and discuss the property
of the phase transition by the generalized Ginzburg-Landau expansion. The
strong external magnetic field spreads this phase over the low chemical
potential region even if the current quark mass is finite. This implies that
the existence of this phase can be explored by the lattice QCD simulation.
