  Let $\Omega$ be a convex domain in $\mathbb{C}^n$ and $\varphi$ a convex
function on $\Omega$. We prove that $\log{K_{\Omega,\varphi}(z)}$ is a convex
function (might be identically $-\infty$) on $\Omega$, where
$K_{\Omega,\varphi}$ is the weighted Bergman kernel. In particular,
$\log{K_\Omega(z)}$ is a convex function if $\Omega$ is convex. We further show
that $\log{K_\Omega(z)}$ is strictly convex if and only if $\Omega$ does not
contain a real line.
