  We report on our calculation of the B \to D^(*) \ell \nu form factors in 2+1
flavor lattice QCD. The M\"obius domain-wall action is employed for light,
strange, charm and bottom quarks. At lattice cutoffs 1/a \sim 2.4, 3.6 and 4.5
GeV, we simulate bottom quark masses up to 0.7/a to control discretization
errors. The pion mass is as low as 230 MeV. We extrapolate the form factors to
the continuum limit and physical quark masses, and make a comparison with
recent phenomenological analyses.
