The present invention provides a transistor element having a laminated structure, the laminated structure comprising a sheet-like base electrode being arranged between an emitter electrode and a collector electrode; at least one p-type organic semiconductor layer being provided on each of the surface and the back sides of the base electrode; and a current transmission promotion layer being formed, on each of the surface and back sides of the base electrode, between the base electrode and the p-type organic semiconductor layer or layers provided on each of the surface and back sides of the base electrode. According to the present invention, it becomes possible to provide a transistor element (MBOT) that is, in particular, stably supplied through a simple production process, has a structure capable of being mass-produced, and has a large current modulation effect and an excellent ON/OFF ratio at a low voltage in the emitter electrode and the collector electrode.