PURPOSE: To reduce the installation space of a polishing device by making a part of a polishing chamber with a front door free to extend with respect to other parts in an apparatus for removing rust or the like attached to the outer surface of a long artrile such as steel pipe.

CONSTITUTION: A subchamber section 10B of a polishing chamber 10 is inserted into a main chamber section 10A, reduced in it and a truck 19 is pulled into the polishing chamber 10 with a door 12 of the subchamber section 10B opened. With the start of the pulling, the subchamber 10B is extended to the main chamber section 10A and upon the completion of the extension, the introduction of the truck 19 into the polishing chamber 10 is ended and the subchamber section 10B fixed as extended. Then, the door 12 is closed. Then, the long article 21 on the truck 19 is turned with a turning roller 20 while a polishing agent is shot onto the long article 21 from a shooting device 11 to remove rust on the outer surface thereof. Thereafter, the truck 19 is pulled out of the polishing device 10 by the reverse operation.