The optoelectronic properties of β-SnWO4 are investigated in details using experiments on thin film generated by rapid quenching and the first-principles quantum calculations based on the density functional theory (DFT, including the perturbation approach DFPT) and employing the PBE and the range-separated hybrid exchange–correlation HSE06 functionals. The obtained bandgap, optical absorption coefficient, dielectric constant, and charge-carrier effective masses for β-SnWO4 exhibit data irreconcilable with the reported values: e.g., a large and direct bandgap of 4.30 eV (UV-responsive), inconsistent with the values in the literature (visible-responsive). These properties obtained for β-SnWO4 are distinctive from those for α-SnWO4: an indirect bandgap of 1.52 eV with higher charge mobilities. These data of intrinsic stoichiometric materials suggest that the literature reported nonstoichiometric materials where defects significantly influence the optoelectronic properties.