  In crystalline materials, electron-phonon coupling (EPC) is a ubiquitous
many-body interaction that drives conventional Bardeen-Cooper-Schrieffer
superconductivity. Recently, in a new kagome metal $\rm{CsV_3Sb_5}$,
superconductivity that possibly intertwines with time-reversal and spatial
symmetry-breaking orders is observed. Density functional theory calculations
predicted weak EPC strength,$\lambda$, supporting an unconventional pairing
mechanism in $\rm{CsV_3Sb_5}$. However, experimental determination of $\lambda$
is still missing, hindering a microscopic understanding of the intertwined
ground state of $\rm{CsV_3Sb_5}$. Here, using 7-eV laser-based angle-resolved
photoemission spectroscopy and Eliashberg function analysis, we determine an
intermediate $\lambda$=0.45~0.6 at T=6 K for both Sb 5p and V 3d electronic
bands, which can support a conventional superconducting transition temperature
on the same magnitude of experimental value in $\rm{CsV_3Sb_5}$. Remarkably,
the EPC on the V 3d-band enhances to $\lambda$~0.75 as the superconducting
transition temperature elevated to 4.4 K in $\rm{Cs(V_{0.93}Nb_{0.07})_3Sb_5}$.
Our results provide an important clue to understand the pairing mechanism in
the Kagome superconductor $\rm{CsV_3Sb_5}$.
