Whether the magnetic field corotates with the magnet or not when a magnet rotates around its own magnetic axis is a problem which is known as unipolar induction and has been debated for a century. Someone thinks that the magnetic field can rotate together with the magnet, but the others don’t think so. It seems that astronomers believe that the magnetic field can corotate together with the magnet (for example, in the pulsar model, the magnetosphere particles are thought to corotate driven by the magnetic field). But general physicists tend to accept the viewpoint of that magnetic field does not corotate with the magnet. Whether does this difference really exist? Who would be so kind as to provide some relative references?