PURPOSE: To grind a workpiece with high efficiency and high precision by a method wherein a jig fitted with the workpiece is made displacable in relation to a grinding tank and thereby the wide fluidity is given to a grinding material.

CONSTITUTION: A jig A to which a workpiece 5 is to be fitted is inserted in a grinding tank 1 displacably in the axial direction. By the rotation of the grinding tank 1, a grinding material put in the tank is given the fluidity. As the grinding tank 1 rotates, the jig A is also displaced, while being rotated properly or irregularly, and, during these rotations and displacement, the workpiece 5 running in friction with the grinding material is ground.