In a magnet cover caulking method of an electric motor, the method achieves caulking and fixation by forming a taper-shaped outer peripheral portion, a diameter of which is reduced toward an outer side in an axial direction, in an outer periphery of a magnet holder, arranging an annular caulking jig in an outer periphery of a rotating shaft, pressing a taper-shaped forming portion a diameter of which is increased toward an outer side in an axial direction, provided in one end side of an inner periphery of the caulking jig to a straight end portion of a magnet cover installed to the outer periphery of the magnet and the magnet holder from the axial direction, and forming the end portion of the magnet cover according to the taper-shaped outer peripheral portion of the magnet holder.