A novel type of organic transistor based on the charge injection at an organic/metal interface was proposed. The device was composed of an organic deposited film sandwiched between the emitter and collector electrodes and the third stripe-shaped base electrode embedded in the organic film. The output current was successfully modulated by an applied voltage on the third electrode, and the current amplification factor, h(FE), reached 25. The operation of the device was attributed to electron injection from an emitter electrode by the accumulation of holes supplied by the third electrode at the organic/metal interface. This device also worked as a photo transistor, in which the sensitivity can be modulated by the base bias.