Sterile neutrino is a decaying dark matter candidate which can be produced non-thermally in the early Universe. Gauged B-L symmetric extension of the standard model naturally accommodates such a sterile neutrino dark matter, and also provides new mediators, B-L gauge boson and symmetry breaking scalar boson. Viable ranges of the dark matter mass and coupling have been studied in this mode. In this talk, we reexamine the freeze-in production of the sterile neutrino dark matter in gauged B-L model. Longitudinal mode contributions in scattering processes as well as inverse decays of the B-L gauge boson and scalar boson are taken into account in our analyses. We will discuss the contributions from these for different mass spectra of the dark matter, gauge boson and scalar boson. Then it is shown that the contributions from these are large and the allowed parameter space is changed from previous studies.