  We report a detailed study of tunneling spectra measured on
2H-Ta$_x$Nb$_{1-x}$Se$_2$ ($x=0\sim 0.1$) single crystals using a
low-temperature scanning tunneling microscope. The prominent gap-like feature
unintelligible for a long time was found to be accompanied by some "in-gap"
fine structures. By investigating the second-derivative spectra and their
temperature and magnetic field dependencies, we were able to prove that
inelastic electron tunneling is the origin of these features and obtain the
Eliashberg function of 2H-Ta$_x$Nb$_{1-x}$Se$_2$ at atomic scale, providing a
potential way to study the local Eliashberg function and phonon spectra of the
related transition-metal dichalcogenides.
