In an elastic wave filter apparatus, IDT electrodes and first and second electrode lands are provided on a first main surface of a piezoelectric substrate. The piezoelectric substrate, a supporting layer, and a covering member define a hollow portion. A signal terminal, a ground terminal, and a heat diffusion layer are provided on a second main surface of the piezoelectric substrate. The first and second electrode lands are electrically connected by first and second connection electrodes to the signal terminal and the ground terminal, respectively. The heat diffusion layer is provided at a position where the heat diffusion layer overlaps at least a portion of the IDT electrodes across the piezoelectric substrate.