  We study the superconductivity in typical $d$-band elemental superconductors
V and Nb with the recently developed non-empirical computational scheme based
on the density functional theory for superconductors. The effect of
ferromagnetic fluctuation (paramagnon) on the superconducting transition
temperature ($T_{\rm c}$), which in principle suppress the $s$-wave
superconducting pairing, is quantified without any empirical parameter. We show
that the strong paramagnon effect cancels the $T_{\rm c}$-enhancing effects of
the phonon-mediated pairing and dynamical screened Coulomb interaction.
