An elastic-wave filter device includes a package substrate and filter mounting pattern provided on a first main surface of the package substrate on which a longitudinally coupled resonator-type elastic-wave filter is mounted, a back-side terminal pattern is provided on a second main surface thereof, and an internal electrode pattern is provided inside the package substrate. When seen in plan view from a direction perpendicular or substantially perpendicular to the first main surface of the substrate body, first via conductors electrically connecting a ground pattern element of the filter mounting pattern connected to a ground pad of the longitudinally coupled resonator-type elastic-wave filter and an internal ground pattern element of the internal electrode pattern are arranged asymmetrically with respect to a center line X-X passing through an input pattern element of the filter mounting pattern and through two output pattern elements.