A vertical organic transistor is disclosed, which includes at least: a collector contact layer disposed on a substrate; a first organic semiconductor layer disposed on the collector contact layer; a base contact layer disposed on the first organic semiconductor layer, wherein the base contact layer comprises no less than two layers of hetero-metal layers or hetero-conductive organic layers; a second organic semiconductor layer disposed on the base contact layer; and an emitter contact layer disposed on the second organic semiconductor layer. Device properties such as output current and Ion/Ioff rate can be improved by using the vertical organic transistor of this invention.