  We study the effect of vertical electric field (E-field) on the electronic
properties of multilayer graphene. We show that the effective mass, electron
velocity and density-of-state of a bilayer graphene are modified under the
E-field. We also study the transformation of the band structure of multilayer
graphenes. E-field induces finite (zero) bandgap in the even (odd)-layer
ABA-stacking graphene. On the other hand, finite bandgap is induced in all
ABC-stacking graphene. We also identify the optimum E-field to obtain the
maximum bandgap in the multilayer graphenes. Finally we compare our results
with the experimental results of a field-effect-transistor.
