Disclosed herein is a spin transistor including: a semiconductor substrate having a channel layer formed therein; first and second electrodes which are formed to be spaced apart from each other on the substrate at a predetermined distance along a longitudinal direction of the channel layer; a source and drain which include magnetized ferromagnetic materials and are formed to be spaced apart form each other between the first electrode and the second electrode at a predetermined distance along the longitudinal direction of the channel layer; and a gate which is formed on the substrate between the source and the drain, and adjusts spin orientations of electrons passing through the channel layer, wherein the electrons passing through the channel layer are spin-aligned at a lower side of the source by a stray magnetic field of the source and spin-filtered at a lower side of the drain by a stray field of the drain.