Use of a spin transistor comprising: a substrate having a channel; a source and a drain, which are made of ferromagnetic material, formed on the substrate to be separated from each other and having identical magnetization directions; a gate formed on the substrate for controlling a spin direction of an electron passing through the channel, wherein the magnetization directions of the source and the drain are perpendicular to a length direction of the channel, wherein in use: the spin direction of the electron reaching the drain is controlled to be parallel or anti-parallel to a magnetization direction of the source and the drain by changing the direction of a spin-orbit coupling induced magnetic field (H eff) through controlling a polarity (+ or -) of the gate voltage, and the spin transistor is turned on when the direction of the spin-orbit coupling induced magnetic field (H eff) by applying a positive voltage to the gate is identical to the spin direction of the electron injected from the source, characterized in that the spin transistor is turned off when the direction of the spin-orbit coupling induced magnetic field (H eff) by applying a negative voltage to the gate is opposite to the spin direction of the electron injected from the source. a substrate having a channel; a source and a drain, which are made of ferromagnetic material, formed on the substrate to be separated from each other and having identical magnetization directions; a gate formed on the substrate for controlling a spin direction of an electron passing through the channel, wherein the magnetization directions of the source and the drain are perpendicular to a length direction of the channel, wherein in use: the spin direction of the electron reaching the drain is controlled to be parallel or anti-parallel to a magnetization direction of the source and the drain by changing the direction of a spin-orbit coupling induced magnetic field (H eff) through controlling a polarity (+ or -) of the gate voltage, and the spin transistor is turned on when the direction of the spin-orbit coupling induced magnetic field (H eff) by applying a positive voltage to the gate is identical to the spin direction of the electron injected from the source, characterized in that the spin transistor is turned off when the direction of the spin-orbit coupling induced magnetic field (H eff) by applying a negative voltage to the gate is opposite to the spin direction of the electron injected from the source. the spin direction of the electron reaching the drain is controlled to be parallel or anti-parallel to a magnetization direction of the source and the drain by changing the direction of a spin-orbit coupling induced magnetic field (H eff) through controlling a polarity (+ or -) of the gate voltage, and the spin transistor is turned on when the direction of the spin-orbit coupling induced magnetic field (H eff) by applying a positive voltage to the gate is identical to the spin direction of the electron injected from the source, characterized in that the spin transistor is turned off when the direction of the spin-orbit coupling induced magnetic field (H eff) by applying a negative voltage to the gate is opposite to the spin direction of the electron injected from the source.