The present invention relates to a magnetic chuck. The present invention provides a magnetic chuck comprising: a lower plate to which a conductive magnetic body for fixing one side of a warped workpiece by magnetic force is coupled; a main body made of a magnetic material and an open side of which has an accommodation groove for insertion of insulating means, the main body being fixed at the lower plate; insulating means inserted into the accommodation groove of the main body and embedded with an insulating coil and an Alnico magnet on the interior thereof, the insulating means being configured to induce a magnetic line of force to flow only through the Alnico magnet to thus provide strong fixing force for the workpiece through the magnetic chuck; and a support member arranged on an upper portion of the main body to be attached to the other side of the workpiece through the magnetic field of the Alnico magnet. According to the present invention, the magnetic line of force flowing from the magnetic chuck is permitted to flow only at both ends of the workpiece so that a grinding and cutting process for maintaining the flatness of the workpiece is enabled while maintaining the shape of the warped workpiece, thus enabling surface processing even at the state where the warped surface of the workpiece is maintained. Furthermore, precise processing on the plane and right angle of the workpiece and precise processing on the right angle of both sides of the workpiece can be performed without using a separate jig, and various forms of processing such as angular processing, rod processing and the like can be easily performed.