PURPOSE: To reduce a time for exchanging a work roll and to automate the operation by driving drive shafts in the direction of spindles to support the spindles and abutting and supporting coupling members on the spindles.

CONSTITUTION: The release operation of a supporting device A is, first of all, to changeover a direction control valve through a manual input and to supply and air pressure signal from an air pressure source to a master valve and a limit valve 15. The master valve is changed over, the air pressure is supplied to the head sides of air pressure cylinders 7, 7 of lock mechanisms, locking bars 8, 8 are turned to a direction separated from the drive shafts 1, 1 to be unlocked. On one hand, when cylinder rods 7a, 7a are retreated a prescribed distance, it is detected by a limit valve 15, the limit valve is changed over to the reverse side and signal is sent to the master valve to changeover the master valve. In this way, cylinder rods 4a, 4a are retreated and the coupling members 2, 2 are separated from the spindles 105, 106 to release the support.