PURPOSE: The kinetic energy is generated by the magnetic force of the shot consisting of the magnetic body such as steel particle and by colliding the shot with the inner and outer surface of non-magnetic tube the grinding method can be improved and the description of the device.

CONSTITUTION: In the inner grinding of a tube 1, the tube 1 is transferred to an arrow direction B by its rotation. In the outside of the tube 1, a magnetic force generating device 4 is installed by the alternating current. A shot loading device 8 in the form of the thread winding bobin is inserted into a magnetic field C of the tube 1 and then, a shot 11 is charged in a space S. The shot 11 is given the kinetic energy vibrating in the magnetic field and repeats the collision with the tube inside for grinding the specified part. The device 8 is made of a center bar 9 which is a strong magnetic body and in the tube 1 transferrence to B direction, it is kept inside the magnetic field