A functional device includes a pair of electrodes 1 and 4 and a macromolecular structure including a hole-conducting layer 5 and an electron-conducting layer 2. The macromolecular structure includes a first hyperbranched macromolecule and a second hyperbranched macromolecule, at least one of the first hyperbranched macromolecule and the second hyperbranched macromolecule has a hole conductivity or an electron conductivity, one of the hole-conducting layer and the electron-conducting layer includes one of the first hyperbranched macromolecule and the second hyperbranched macromolecule, and the macromolecular structure has a self-assembled structure formed by a non-covalent interaction via the first hyperbranched macromolecule or the second hyperbranched macromolecule in at least one of the hole-conducting layer, the electron-conducting layer and the interface between the hole-conducting layer and the electron-conducting layer.