  We calculate the rho meson mass in a weak magnetic field using effective
$\rho\pi\pi$ interaction. It is seen that both $\rho^0$ and $\rho^\pm$ masses
decrease with the magnetic field in vacuum. $\rho$ meson dispersion relation
has been calculated and shown to be different for $\rho^0$ and $\rho^\pm$. We
also calculate the $\rho\pi\pi$ decay width and spectral functions of $\rho^0$
and $\rho^\pm$. The width is seen to decrease with $eB$ and the spectral
functions become narrower.
