  We investigate the electromagnetic properties of the deuteron such as the
charge and magnetic form factors by solving the Bethe-Salpeter equation (BSE)
with the separable ansatz. In solving the deuteron bound state solution to the
BSE, we include negative energy components of $P$-wave in addition to the
$^3S_1$ and $^3D_1$ states of positive energy, employing a rank IV separable
ansatz. We found that the inclusion of the negative energy components improves
systematically the electromagnetic properties which are not described in the
conventional non-relativistic impulse approximation.
