  We first extend our formulation for the calculation of $\pi$- and
$\sigma$-meson screening masses to the case of finite chemical potential $\mu$.
We then consider the imaginary-$\mu$ approach, which is an extrapolation method
from imaginary chemical potential ($\mu=i \mu_{\rm I}$) to real one
($\mu=\mu_{\rm R}$). The feasibility of the method is discussed based on the
entanglement Polyakov-loop extended Nambu--Jona-Lasinio (EPNJL) model in
2-flavor system. As an example, we investigate how reliable the imaginary-$\mu$
approach is for $\pi$- and $\sigma$-meson screening masses, comparing
"screening masses at $\mu_{\rm R}$ in the method" with "those calculated
directly at $\mu_{\rm R}$". We finally propose the new extrapolation method and
confirm its efficiency.
