This disclosure provides a technique that prevents debonding at an interface between a functional device and a resin on reflow soldering in a functional device-mounted module requiring a hollow structure. Also disclosed is a functional device having a functional portion mounted on a substrate formed with predetermined wiring patterns, wherein the functional portion of the functional device is arranged in a receiving space, and the substrate is provided with a hole which communicates with the receiving space and a solder-introducing portion made of a metallic material compatible with solder. During solder reflowing, the functional device-mounted module is placed on a mounting substrate such that the solder-introducing portion of the functional device-mounted module contacts a solder paste, and solder is melted with heat. Water inside the receiving space is thus discharged, and solder is introduced into the hole due to surface tension, and the interior of the receiving space is sealed.