Our model of molecular electronic devices with functional groups is introduced. This device would function as a diode and photo-switching device based on biological vectorial electron transfer (ET) system. Shown next are strategy and experimental results toward the model realization using Langmuir-Blodgett (LB) films, cytochrome c and artificial flavocytochrome c. We have analyzed cyclic voltammograms of flavin-porphyrin LB heterolayer-modified electrode and found that vectorial ET occurred between flavin and porphyrin. Vectorial ET was also found to occur between flavin and cytochrome c by electrochemical methods using a flavin LB monolayer-modified electrode in cytochrome c solution and using an electrode modified with two-dimensional crystal of cytochrome c on a flavolipid monolayer. These results of the vectorial ET between flavin and porphyrin have opened a door to the construction of molecular electronic devices.