A spin transistor includes a semiconductor substrate including a channel layer having a 2-dimensional electron gas structure and upper and lower cladding layers disposed respectively in upper and lower sides of the channel layer; ferromagnetic source and drain electrodes formed on the semiconductor substrate and disposed spaced apart from each other; a gate electrode disposed between the source electrode and the drain electrode and having a gate voltage applied thereto in order to control the spin of electrons passed through the channel layer; a first carrier supply layer disposed between the lower cladding layer and the channel layer to supply carriers to the channel layer; and a second carrier supply layer disposed between the upper cladding layer and the channel layer to supply carriers to the channel layer.