  The renormalization group method is applied to the three-loop effective
potential of the massive $\phi^4$ theory in the $\bar{\rm MS}$ scheme in order
to obtain the next-next-next-to-leading logarithm resummation. For this, we
exploit four-loop parts of the renormalization group functions $\beta_\lambda$,
$\gamma_m$, $\gamma_\phi$, and $\beta_\Lambda$, which were already given to
five-loop order via the renormalization of the zero-, two-, and four-point
one-particle-irreducible Green's functions, to solve evolution equations for
the parameters $\lambda$, $m^2$, $\phi$, and $\Lambda$ within the accuracy of
the three-loop order.
