An aroma-diffusing heating device includes a heating base, an aroma capsule detachably accommodated in the heating base and heatable by the heating base to give off fragrance, and a cap capped on the heating base over the aroma capsule. The aroma capsule includes a heat-transfer container defining a top opening, an aromatic substance held in the heat-transfer container, and a sealing film bonded to the heat-transfer container to seal the aromatic substance in the heat-transfer container.