PURPOSE: To make a universal mill convertible to other rolling mills as well if an intermediate housing is changed by disposing freely attachably and detachably chock parts into the intermediate housing while the rolling rolls built in a chock assembly for double rolling rolls are held in a vertical or horizontal position.

CONSTITUTION: A universal rolling mill is converted to a horizontal double rolling mill if an intermediate housing 1 contg. vertical rolls 16 of the universal rolling mill is changed to an intermediate housing 2 for the horizontal double rolling mill. More specifically, upper and lower horizontal chocks 7, 12 set with rolls 6, 11 in a horizontal position are disposed at the top and bottom of the housing 2 and are made into one body by means of a prestressing rod 19 and a prestressing cylinder 20. The universal mill is converted to a vertical double rolling mill as well if the housing 1 contg. the vertical rolls 16 for the universal rolling mill is changed to an intermediate housing for a vertical double rolling mill.