The present invention provides a permanent magnet, comprising a cylinder formed with a permanent magnetic material. The cylinder comprises along a radial direction, a magnetic core and a magnetic sheath that are coaxial. The magnetic core is assembled in the magnetic sheath. The magnetization direction of the magnetic core is axial direction, and the magnetization direction of the magnetic sheath changes step by step from a direction which is parallel to the magnetization direction of the magnetic core in one end to a direction which is orthogonal to the magnetization direction of the magnetic core in the other end, along the axial direction of the cylinder. Moreover, a magnetic device for use in MRI using the magnet and manufacturing methods for the permanent magnet and the magnetic device are also provided in the present invention. With the permanent magnet, magnetization strength in the working area generated by the magnetic device for use in MRI can amount to more than 0.5-0.6 T.