PURPOSE: To apply a proper rolling motion to the content of a container and to satisfactorily arrest the content by closing both ends of the container having a filling opening on its circumferential wall, and forming at least one of two closure walls with a rotary plate.

CONSTITUTION: A rotor is provided to be rotated relatively to a container 4 arranged horizontally and having a filling opening 27 on its circumferential wall, the container 4 is rotated by this rotation of the rotor, and its content is rolled. Both end closure walls of the container 4 are formed with rotary plates 5, 6 driven in the same direction or opposite directions. A proper rolling motion is applied to the content (workpieces and abrasives) of the container 4 by the rotary plates 5, 6, and the filling factor of the container 4 is increased.